Good place to start is turn them both in and turn them both out 2 turns. Also turn the idle screw out.
Start the machine if it does not idle turn the idle screw up. Pull the throttle lever and if it does not accelerate quickly turn the L screw out a 1/4 turn. Once the thing accelerates smoothly and quickly let it idle. if it does not idle turn the idle screw in until it does.
Run the thing at full throttle and slowly turn the H screw out until it starts to slow the rpm. The motor should sound like it is running a little rough. screw the H screw in 1/16 of a turn at a time, let the thottle off and throttle up and hold. Keep doing this until the engine sounds rough 1 in 10 seconds. Your almost there... one final 1/16 of a turn should do it.