I assume that you've already got an email account which you're currently accessing via the web, rather than through an email client such as Outlook Express.
Further, I also assume that it's an account provided by your ISP (or another provider) which does support the use of programs such as Outlook Express. (Some free web-based mail systems, such as Hotmail, don't allow you to use Outlook Express).
If that's all correct, you need to know the following information:
1. Your email address
2. Your password for your email. (If your email is provided by your ISP it might well be the same password that you log onto the internet with, but this is not always the case).
3. The SMTP and POP3 server addresses for your ISP (or other email provider). Don't worry if that sounds complicated, it's not. The relevant information will be on the support pages of your ISP's (or other email provider's) website. However, if you're with one of the big UK ISPs, you can find the information more quickly by looking here:
http://www.idl.uk.com/email/isp_settings.htm
Now open Outlook Express and set up your account by going to Tools > Accounts > Add > Mail, and simply follow the wizard.
To check that it's working, click 'Create Mail' and address an email to your own address. Then click 'Send'. Wait a minute or so, then click 'Send/Recv'; the mail should arrive in your Inbox. After that, everything is fairly intuitive. Just post again if you're confused.
Chris
PS: If not already got a suitable email account,to use with Outlook Express, follow my instructions in paragraph 3, et seq, here:
http://www.theanswerbank.co.uk/Technology/Inte rnet/Question407429.html