The best way to do this is on the ice if you can, and have some one help you hold it. I included a pic of my carb, the left screw is the low speed needle mixture and the right screw is the high speed needle mixture. What I found on mine is even when adjusted to the max rich settings CCW it would still be running lean and quit after idleing just a few second unless I pressed on the primer bulb. The carb needles richen the fuel mix by turning them CCW or out. Leaning the mixture by turning them CW or in. Those red cap are just press fit on, I took them off to get enough adjustment. You will need a small flat blade screw driver to ajust the needles.
I started by getting it running and warming it up. Then run a hole and adjust the high end needle until the it's running clean. It's hard to describe the sound, if you richen up the high speed needle while drilling a hole you will start to bog down. What you want to do is lean the high speed needle to where it's just running smooth while drilling. Problem some get into is as you lean out the mixture your rpms will increase and some over do it. You just want the engine breaking in to the where it's running smooth.
After that, you will probably have to richen up the low speed needle to get it to stay idleing. Small adjustments is all you need as the needles can be sensitive. After this adjustment punch another hole. When excellerating the motor if it bogs you may be a tad rich on the low speed needle and the carb is starting to flood the engine, if it stumbles it's a little lean yet. This is the norm but not always, Keep making small adjustments, then run another hole and let it come down to idle.
Contrary to some you will need to go back and forth between the needles until you get it. I believe I added a 1/4 CCW "richen" turn past where the plastic stops were on the low speed needle. The high speed needle needed to be lean just slightly.
After getting it set I put the plastic red caps back on and put them in the center position. I've adjusted many 2 strokes and they can be touchy, I spent all of 15 mins on the ice getting mine to run. One other note, all engines need some run time on them to break-in, usually a tank should do. You may find your self adjusting your carbs again as the engine breaks-in, I haven't had too yet. Also, make sure your oil mix is correct, too much oil can be just as bad as too little.
This is my second year with my Jiffy 3hp stealth and it runs great. I hope this helps.