Someone tell me how to use it, and what to use it for, and the kind i should get if i need it. Thanks.

 

Generally speaking, clay is used to get out some embedded dirt/grime out of your paint.
Go to Mother's site and check out the video on their Claybar kit. It's a good kit to start with. Lube as much as possible. If the clay ever "grips", you need more lube. You can also use regular car wash shampoo mixed with water in a spray bottle.
http://www.mothers.com/reelworld/
HTH

 

Just to touch up on what SK2003TYPES said, besides claying you will have to wax your vehicle after you use the product it comes with a small bottle of it. The clay is also good for the windows like over spray from a body shop at least that is what i used on my windows and it came out, i try to clay it twice a year once before the winter and once after. There is alos another clay bar i use it is called blue magic, its pretty good but i like mothers better.

 

Read this article:

http://www.properautocare.com/usclaybartor.html