No worries. This is very basic information and there is a plethora of it about on the net and on these forums, please read stickys and use the search feature of the forum before posting ;-) As this has been answered before many times over.

However, it all depends on the high/stoned you particularly like.. if you like a really strong body high then use the magnifing glass to see when 90% of the trichomes are cloudy/amber colour, if you want a less strong body high and a more uppity and buzzy high then harvest when 30/40% trichomes are cloudy/amber.

Check youtube for pictures/videos of what this is like, like i said, its up to you depending on the high you like and there is loads of info about this. Use us to reinforce what you've already researched, not use us for your research whilst you sit back and get stoned

Good luck!