Depending on what version you have it can mount different ways. (Side mounting, weaver...)
I'm guessing you have a traditional side mounting sight. You need to make sure your AK has a side mount. (On the left side, looking from the rear.)
I'm guessing that is the problem, as once you have the mount and the sight... Its really simple. Slide in and lock.
You'll need advice from someone else on getting the mount, and installing it... I have not yet, although I plan too eventually...