The primer is just beside the glass bowel. Unscrew the round handle and pump 5-10 times up and down before starting and then tight it again.
When you saying "cranks quick sometimes and is a little stubborn sometimes" do you mean that the engine starting "firing" quick sometimes .... If so, can you see a different if the tractor has been standing for a while, cold, warm.. . When it's stuborn dose it firing on any cylinder and after a while the others also start? The problem can then bee that the fuel has flown back to the tank, that could happen if there is a minor air-leak in the system. If it helps to pump, this might be the problem.
If you mean "cranks quick sometimes and is a little stubborn sometimes" that the starter turns the engine slow sometime you have to look at the starter or battery.
Hazze