Hey
Go to the 'Editors Depot' part of this site (3rd link along at the top of this page) u will find all u need to know there!
I have been editing for about 2 weeks and i am just about wrapping up my first map ;D
I would recomend u take a peek at 'Johan Gustavson's guide to editing' and 'Abuu' s guide to editing' but first check out MacGuba's 'Beginers guide to editing' as this starts from the bare bones of the editor
It can be quite daunting at first when u start to read about scripting and stuff but u will be suprised how easy it can be and if need be u can always copy and paste the scripts in the tutes and from the script snippets board but be sure to acknowledge the creator of anything u have used in the readme on your map
And of course if u get stuck,
ASK, that's what the forums are for ;D
Happy editing