Go into HOSTING & DOMAINS and then click on FILE MANAGER and then you should have you HTM pages listed there....
There is a EDIT coloum on the list and a icon beside each page which if you click, will let you edit the html of the page (there is also a visual editor on this page too)
All of these suggestions are possible, but without an address (URL) to look at, it's all speculation. Give us an address to look at, and we may be able to tell you a little bit more about how to edit you inherited pages.