Welcome to the Deep Rock Galactic modding readme!
To install mods, open the game and go to the modding tab on the esc menu.
From there click the install button and browse to the mods you want to install. Click subscribe to install a mod.
More info can be found here: https://drg.mod.io/ 
If you want to make mods for the game, info can be found here: https://drg.mod.io/guides