I'm glad you've rediscovered the sims and are having fun with it
First, if you haven't already, you'll want to download the zip file at the bottom of the first post in this thread, called "TDK-Joker.Sims2Pack.zip"
There are potentially two types of files you're going to find in any zip/rar file containing custom content; .package files and .sim2pack files. The first (.package) get extracted into Documents/EA Games/Sims 2/Downloads. If you don't have a Downloads file, you can go ahead and create on, but make absolutely sure you spell the way I am spelling here. Downloads. Plural with a capital 'D'.
The second type (sims2pack) of file is the format you'll find just about every sim and house you download. You can double click on them and they'll self install into your game, but you could run into problems if the creator has EPs you don't. A good way to get around this is to download and install the
Clean Installer. This will install sims2packs and let you see everything in the file. As I said before, this is useful for downloading sims made with EPs or SPs you don't have.
Once the sim is in your game, you can find it in game by going into CAS and clicking on the sim bin button on the console. It's the icon that has a group of six stylized humanoid figures. This is where you'll also find the sims you made in Bodyshop.
Hope that helps.