simple

own the game on steam

all pc versions of mcc support mods but you will need to go through a bit more of a process to get the mod loading. we created a mirror of the files on nexusmods so that non steam players can access it.

https://www.nexusmods.com/halothemasterchiefcollection/mods/2640

there are install instructions in the description. these install instructions also work for any other workshop mod provided you can find a way to download them (valve doesn't seem to allow third party downloads of workshop content)