Start it up, let it warm up some....then open the throttle ALL the Way (on the Quadrant)..then close the Main fuel screw until it labors and/or backfires, then open it back up 1/2 turn ( approx)..
How much depends on whether you are working it Hard ( more), or light..(less)...and I KNOW what I am talking about...!
These nearly always need copious CHOKE, to keep the fire lit until they warm a little.!
Idle, just find the "best" idle and leave it there...