Here's the crank puller you need:
Also, you probably will need a regular 8mm allen wrench or a 8mm allen socket to remove the crank bolt. I don't know if you can get enough leverage with the Alien multitool 8mm allen.
Once you remove the crank bolt, you use the above linked crank puller to pull off the crank arm.
How it works is the crank puller outside is screwed into the threaded crank arm. Then when you turn the handle, inside shaft pushes against the square shaft of the bottom bracket and the crank arm is pulled off. When reassembling you should have a torque wrench that will do 350 in-lbs and an 8mm allen socket. It's important to torque the crank arms to the tapered bottom bracket shaft.