Where should I attach the blower motor leads on a Payne air handler?
Blue is a speed tap and yellow is common or L2   There should also be a red and black wire coming from the motor that should be capped off unless the motor has been changed. 
A picture of the board and wiring diagram would help. It looks from the very poor wiring diagram I found that the yellow wire would go to K1 and the blue would go to NO but like I said the diagram wasn’t very specific.