It's far from stupid--just the opposite. Not sure why you are having trouble since the app's description explains it is like Crayon Physics. Google it and perhaps you'll have a better understanding of what's going on in iPhysics.
Once you have iPhysics installed, you need to start getting level packs available in installer in the iPhysics folder.
I install 2-3 at a time and play them all till I can solve them fairly easily, then uninstall them and get some new ones. There are a TON of levels out there. some are easier than others, but all of them are fun to play. I even got my wife addicted to them. hehehe slowly bringing her around to getting an iPhone...
this game is a life saver.. very unique and a game that involves thought! i play it all the time during my ap environmental class. love all the different level packs, JungZandvliet and Rawd's Multimap are my 2 favs