Before you start using the program you need to configure the keys you want use. By default you use the arrow keys to move the cursor around, A to left-click, S to right-click, and Caps Lock to alternate between using the keyboard and mouse.
Despite how it might look at first, using the keyboard to move the mouse can actually be pretty comfortable. For instance, when you move the cursor over a place where you can write, it shows it to you automatically, and just by clicking on that white space you can start typing with the keyboard as usual.
MouseFIGHTER is a pretty interesting application that's definitely worth trying out.