Open Outlook Express (assuming that's your mail client).
Click Tools/Options
Click on the Send tab
In the section "Mail Sending Format" Click on HTML
Click OK
Just realised that your question is rather ambiguous: the instructions above are for sending your e-mails as rich text.
If you have been advised to READ your e-mails as rich text, then:
Click Tools/Options
Click on the Read tab
Uncheck the box "Read all messages in plain text"
plus....... if you've been told this because you don't see pictures in the mails you receive and you still don't, also check the security tab and make sure that "Download Images/Block images and other external content in HTML e-mail" is not ticked.
Thanks for all your replies, couldn't answer before and couldn't sign in (I'd been messing with the settings!!) When i went to Compose I found a Rich text in small print, so clicked on it and there it was. Thanks very much anyway guys!!