Don't worry, fiddling about is how you learn stuff. Start the bike up and warm it thoroughly for about 10 minutes until the choke is completely off. Now hold the revs at about 1400 - 1500 rpm using the throttle, and turn the tickover screw clockwise until the revs stabilise without you holding the throttle. Slowly turn the screw anti-clockwise until tickover settles around 1100 rpm. When starting from cold open the throttle slightly even with choke, or if that's what you did try it without throttle and just choke. Some bikes need one way some the other!!