Welcome aboard!
You'll need to 'mount' the pods for them to work in the game. If I may I'll paste a reply I wrote not long ago (links included):
>> 
My question is, what program do I need to get all the trucks and tracks into the game?
None, or one of many. The "
pod.ini" in your game folder is a text file that lists the pods 
mounted in your game, if they're not listed there they won't be available in the game. You can edit this list by hand or you can use any number of utilities to help you easily add your files to it. I'd recommend 
Cowpod.
Understand that there is a limit of 30 mounted pods after a fresh install of the game but once you apply the 
patch you can mount up to 99 pods. However, you should generally avoid mounting too many pods all in one shot so you can monitor problems or conflicts, and if you encounter errors remember 
this link.