Very easy to do my friend.
http://newfreshpeace.blogspot.pt/2012/12/turn-normal-webcam-into-ir-webcam.html
By the way, you might see a small piece of glue on the lens (to not allow it to unscrew itself). If you can unscrew it, get a small knife and a magnifier glass and rip it off carefully.
The filter is inside the lens when you remove it. Do it gently with a precision screwdriver or something alike.