how?!

Using ZQuest (if you're using windows, its ZQuest-w.exe)
I suggest doing a short 3 dungeon quest in classic tileset first to familiarize yourself with how it works first.
If you mean how to build various aspects, there are lots of people who are better at explaining it than me, try one of these links:
Help forum here
PureZC help forum
PureZC design forum
Also, check out the wiki: ZCwiki
Hopefully this helps, and welcome to Zelda Classic?!

(yeah, it seams kinda dead around here nowadays... )