How can I insert HTML coding into a menu on one site of the page?

Forgive me if this is in the wrong spot in the forum.  I'm new to Joomla.

Currently, when I click my forum link, the forum appears on the main body of the page with the navigation menu on the left hand side.  Is there a way to when I click on forum that there is no navigation structure and that the forum takes up the whole body of the page?

Thanks for you help...