It just slides onto the crank. I'm assuming you have the bolt out?
Over time, the crank and pulley kind of fuse together and then you have to use a 2 bolt puller to remove it. You can borrow these pullers from just about any major part store - they're only about $20, so I just bought one.
^ impact gun!!! i used a steering wheel puller to remove mine. thread into two holes in pulley and i used the impact gun for the rest as well takes about five minutes. other things i tried before the gun were useless and wasted an hour or two trying.