That is an easy part mate. It's just a bolt into a hole with a spring on it. You won't do any damage by altering this - it's purely an idle adjuster and will not change any fuelling, etc. The only thing you have ot be aware of is turning it the right way as if you go too far the wrong way (anti-clockwise) you will un-screw it out and will pop out with the spring on it so may struggle to get it back in..lol.
Start the car up then slowly turn it clockwise - you will hear the engine revs increase as you turn (may take a few twists before it starts to alter) then set it around the 900rpm mark.