I found this :
### If you want to display most recent ad's, enter the amount of them you want to display

### Recent ad link layout

I need to know what <!--?--> to place on all the pages I want it to show up on.

The <!--LAST--> tag will go in the dispcat.htm template.

Is the dispcat.htm template the only template I can place that at?

Yep. :)