Thank you for downloading GPL Trainer.
The current version of this application is v0.9.
Testing has been minimal thus far, so expect bugs.
I would recommend that you use a PlayStation controller, but just about any controller would probably be better than trying to use the keyboard.
That being said, there are keyboard controls in case you don't have any controllers lying around.

WASD - D-Pad
IJKL - Face Buttons
R - Select
Y - Start
Q - L1
E - L2
O - R1
U - R2

Some actions require the use of the mouse.

Also, there might be some code or something that you can type into the title screen. I'm not sure. It might've started with "down" and ended with "start"?