How Do I Import/Install Hacks, Upgrades and Applications? Plz Assist.

[deadhook1]

There are some hacks and upgrades I'd love to utilize on my site, but am somewhat green when it comes to this stuff.

Once I've downloaded the program or application in questions, how do I Import and Install it into my site?

I saw something about the "product manager" but am not sure where/what that is.

I'd be very appreciative if someone could give me the quick rundown on what I do to get an application installed and working once I've downloaded it.

Is there somewhere specifically I need to download it to or just anywhere on my hard drive?

THANK YOU VERY MUCH FOR ANY ASSISTANCE!!!!!!!!!!!!