1) De-Pbo the mission , see how it was done and then amend/edit it until you have what you want
2) Ask specific questions as you progress through the mission making cycle here in the forums.
3) Refrain in your questioning things like
"I want a whole script system making that will do so n so"
4) Download the official comref and read through it
5) Scrutinise a lot of Ofpec posts, there is a very high chance your question has been asked and answered several times in the past
6) Tools required for your first mission:
.....a) Windows "Notepad" for scripting
.....b) A De-PBO Tool (see editors depot)
7) Reference Materials required
.....a) Comref (OFP "Command reference") (see editors depot)
.....b) Any Tutorials you can find for basic stuff (see editors depot)
The more you help yourself and the more specific your question the more likely you are to get a good response
Good Luck!!