i'm pretty sure this is how u do it.
u get rezinject, fin guns_M_PV_melee and then add ur superknife file on to it and click inject. go to ur ca folder, open it, and find ur Guns_M_PV_melee file. there should be a file nxt to it with .reznew rename that to . rez and either delete the old 1 or rename/ put somewhere els for backup