This is a very common problem, often The Sims 2 installation doesn't automatically create Downloads & Saved Sims folders, which are required for installing most custom content.

Its very simple to fix. Find the following folder on your machine

Right Mouse Click in a space in the folder Window, from the menu that appears choose 'New'

From the second menu choose 'Folder'

This adds a new folder to The Sims 2 directory.

Obviously it wont help much if its still called 'New Folder' so type Downloads into the text box (or right click, choose 'Rename' from the menu).

Remember! Its

Downloads

Not.... downloads or download or Downlaod. Or any other random variant! Make sure you spell it correctly because it does matter! Once you have created this folder, you can simply add the package files you've unzipped as per the instructions. If you're not sure what to do with files you've downloaded, just hit back to select the topics on adding downloads to your game from our FAQ page.

To create a Saved Sims folder to add your clothing, genetics, make up and hair, body and accessory meshes simply repeat the process but rename the folder 

Saved Sims