On the Customize & Resize step, you can access the Crop tool either through the Prepare Your Designs to be Resize Accurately button or in the Customize tab.  

There's no free-hand cropping tool for cropping to irregular shapes. But you can load your design into the Designer (requires the Designer or Pro version) and use the Eraser to wipe out the areas you don't want. To do that, at the Customize & Resize step, click the Customize button and then Designer.