I have enjoyed seeing all the add ons for Civ 4. However I'm not sure how to load them into the game after I download them. How do I add the Scenarios and Mod packs to the program so I might play them?

Welcome to Civfanatics :)
Most mods will come with their own installer or a readme that tells you how to install them. When you start a game you just need to click on load mod (advanced - then load mod) and chose the one you want to play with.
Scenarios are similar, just that you need to click play a scenario (single player - then scenario)...

Ori,
Thank you for the information. I will attempt to play one and see what happens.:)