Modthesims2 help?

Right, I've created an account on "modthesims2.com" and I've gone on downloads and clicked download on an object/terrain etc that I want to download, then it asks me where to save the file. Since I don't really know, I just saved it into any Sims2 folder (lots, savedsims, projects,... etc). And the things I download do not have any other expansion pack for the sims2 on them (i only have the sims2). So when I go on the Sims 2, the things I have apparently downloaded are not there. Any help on how to actually get them on my game?