Here how a chain tool work


*Important don't drive the rivet all the way out. If you drive a normal river it all the way out it's PITA (next to impossible) to put it back in.

Here some step by step picture
http://www.instructables.com/id/Usin...ke-Chain-Tool/

If it's a normal chain without special rivet any rivet will do so you can start anywhere on the chain.

Here a video

http://www.youtube.com/watch?v=OJhereGT9Iw

EDIT: As you may have notice or not, none of those chain has master links