It's not tough to go to the
Apexi Website
and click on
documentation
If it's a reg. safc you'll need to look in 3 seperate PDF's.
S-AFC Wiring Manual
Now that manual only has JDM wiring diagrams so it's good to look in the manual called:
S-AFC U.S. Update
Learn how to use it by reading:
S-AFC Manual
A quick google search of
"SAFC 240sx Install" found this great site which makes looking a the above useless
http://web.ics.purdue.edu/~tmerrick/240SX/apex_safc.htm
Now if you have the SAFC II (The one with the knob instead of the 6 buttons)
S-AFC II Wiring
S-AFC II Manual
Hope this helps.