Okay this could get greekish here
Photopost Classifieds comes with an external script inc_ads.php which displays either the most recent,random or most popular ads and can be included on your forumhome template. This is included in our software by default.
If you want to have 3 separate ad blocks each pulling different ads from specific categories showing in 3 separate ad blocks then you would need to have someone design those for you since it would not be native functionality in the code.