is sleeping from 4:30 to 6 (an hour and a 1/2) enought time??[/b]
it might be enough. As long as its 7+ hours, you should be fine, but over 7 hours is the ideal amount of time since your REM is longest then.

what EXACTLY are u supposed to do during this hour an a half of staying up?? was i correct?[/b]
just occupy your mind about lucid dreaming like reading about it and the techniques, also do some affirmations saying "i will have a lucid dream" while you are walking around