Most, if not all of the settings you change on the server which hosts your website are done in the Hosting Control Panel (henceforth referred to as just HCP).

The HCP is the main place to go when you want to make changes on the server(s) that actually host your domain name, it is used to perform tasks like creating / changing your email settings on the mail server and for many other uses like database creation / modification.

The internet location and login details to access the HCP will be in your Hosting Settings / Welcome email.

Before you setup your email addresses on your computer you must set them up on the server, so that mail can be delivered from other internet servers and so you can collect your mail.
Once you have logged in to your HCP you can setup your email addresses in the "Mail" or "Remote Mail" sections, for more details on how to setup your email addresses please check the FAQ / Knowledge Base of your Web Hosting company or contact their Tech Support staff.

Once you have setup your email addresses on the servers you can immediately access your email using the Webpage based interface at:

http://webmail.trialaccount.com/

When logging in, use the following format (adjust username accordingly)
username@trialaccount.com
The password is what you specified when you created the email address in the HCP.

Or you can setup email software such as Microsoft Outlook with these details:

Email account type: POP3
POP3 / IMAP (incoming) server: mail.trialaccount.com
SMTP (outgoing) server: best to use your ISP SMTP server OR alternatively mail.trialaccount.com

Username: username@trialaccount.com
Password: As set for that email address in the HCP.

Before you can upload / publish your new website you must have the webpage content. If you do not have any content yet, there are many commercially available tools you can use to create it, as well as many free authoring tools.
If you do not wish to create a site from scratch there are also many websites which offer completely free website templates, as well as some that offer templates for sale for various cost. In either case, once you have a website template you can use it as a starting point or use it just as is with some modification to suit your needs.

A few addresses to get you started are:

Website building / editing software
http://www.pagebreeze.com/
http://www.virtualmechanics.com/products/dwarf/
http://www.adobe.com/

Website Templates
http://www.freewebsitetemplates.com/
http://www.websitetemplates.com/

Once you have your website ready to upload to the web, you will need some "FTP Client" software to connect to the server which hosts your webpages and then upload / publish your content.
You should be able to use any FTP software you like, if you do not already have some or are looking for something new, FileZilla is a very good and completely free solution.

To connect using FTP you will need all the details in your Hosting Settings / Welcome email, the details you need are usually:
The FTP Server Hostname : ftp.trialaccount.com or just trialaccount.com
as well as the FTP username and password.
TIP: You can also check and reset your FTP username and/or password in the HCP.

Once you have connected using FTP, all your webpages need to be uploaded to the httpdocs/ folder , with any CGI scripts to the cgi-bin/ folder.
NOTE: When you upload your website you will likely overwrite this file (index.html) so you may wish to take a copy of it or rename it before you upload your site, so you can refer to it later.

*** This section only applies if your hosting package supports SSL (https:// mode) ***
SSL Encrypted pages:

If you have any webpages that need to be secured with SSL then they may need to be uploaded to the httpsdocs/ folder instead, however this requirement varies from server to server.

If you are unsure which server type your domain is hosted on then you can just try to view a single image you have already uploaded to your httpdocs/ folder but use https:// in the address bar of your web browser instead of the normal http:// 
If the image displays in https:// mode then your SSL encrypted content is coming from the same location as your normal webpages. If not then you will need to upload all your SSL secured content to the httpsdocs/ folder only.

Subdomains
When you visit http://www.trialaccount.com , technically the www. part is considered a subdomain. You can use subdomains to organise your site so specific sections are kept seperate to the main website, such as members.trialaccount.com or downloads.trialaccount.com and so on. You may be able to create only a few subdomains or up to an unlimited number, depending on the limits that are set for the hosting package you have.

See http://www.forbeginners.info/web-hosting/subdomains.htm for further information about subdomains.

Web Statistics: Your hosting package also can have the option of web statistics included, with such things as the number of visitors you've received or the search engines people used to get to your site. Usually you will have the option of at least these two statistics generators:

Webalizer - for more info please see the Webalizer homepage:
http://www.mrunix.net/webalizer/

AWstats - for more info please see the AWstats homepage:
http://awstats.sourceforge.net/

Password protected directories
You can also password protect certain directories / folders to keep certain content safe or viewable only by specific visitors. Upon setting a directory password, anybody that tries to visit that location will be prompted to enter their username and password prior to being allowed to view the content.

Custom error documents
Custom error documents allow you to display customised error pages which can display helpful information to your visitors in the event of an error occuring, instead of the standard webserver error pages which usually only contain an error code and a brief description.
An example of an error you could come across is a 'page not found' (404) - using custom error pages you could direct your vistors to your home page instead or to a contact form page so they can let you know about the error.