Here and here the rules are explained in details.

The game is similar to Go. However, there are no 'eyes'; the group of dots is safe when it is connected with the boundary of the board. Dots ('stones') are never removed. There are some other differences, but the rules are pretty easy (simpler than in Go), so you may just try! One of the variants may be played on in a browser (no downloading/installing needed).
In the stand-alone program there are now 2 other variants of the rules to choose from.