It really would help if you would tell us what you need help on, and then we could point you into the direction of those particular things.
Mainly the first thing you should do is download HEK (assuming you did already)
Next thing is to watch a basic tutorial on modeling/texturing/getting things ingame/populating/building map.
Other then that, you should be a bit more specific.
Also, this should help alot.
http://hce.halomaps.org/hek/
That is your best tool of information around when building a map to be honest. (other then actually talking to people who know alot of the stuff)