Please login at the right to update text from the website itself (frontend). After you login click on the icon to the upper left of the text you would like to edit. This will bring up and editing window. Edit it, "save" it, and view your changes. Voila!
If you need to access the Joomla 1.5 back-end administration area to edit/add other items go to this address and login (same login username/password):