How do I remove this crank?
You would need a crank puller. On the left crank remove the bolt, then the crank puller screws in to the threaded part of the crank (black part of crank puller in picture below). You tighten the center part of the crank puller and it slowly pulls the crank from the spindle. 

The same goes for the right crank, from the picture you've posted you first have to remove the cap using a wide screwdriver or thin coin.



You can find crank pullers on ebay quite cheaply or go to your local bike shop.