Plutonium

I was wondering how to install mods, specifically the Co-Op mod for bo1 campaign. Let me know if you guys figured out how to do it

Try this, I found it on a youtube video and it worked for me

do /resetStats at the main menu, restart your game.
Upon relaunching, then try to put the unlock all back into the console (provided in description), once at your desired rank, make ONLY ONE custom class to test. Join into a server, and see if it sticks. If you can choose your custom class with your rank set to whatever, then you're good to go. This is what worked for me, even when I tried setting myself to 14th 27. Here's the unlock code I used for my rank : /statsetbyname rank 27;statsetbyname rankxp 286501;statsetbyname plevel 14;statsetbyname codpoints 2500000;updategamerprofile;uploadstats2.