You're adding the weapons, pistols, nades etc. which you want to use ingame from our Hack Menu which appears after you have injected the hack. There is a big list with all weapons, pistol, knifes, nades etc. etc. which you can use. After you have added them to your inventory, you'Re turning on the inventory hack with only 1 tick in a box above those list.
Later when you look in your inventory there are all items which you have chosen. You need to turn the inventory hack on + inject blueviper(coldhack) everytime if you want to use this inventory hack.
(I can't give you detailed information about server-sided weapons etc. you need to wait for ColdCristal, but his answer may delay, check ->
http://www.coldhacks.com/forum/viewtopi ... 850#p35850)