You should buy a copy: Steam or Paradox
For packaged versions of these mods see Steam, Nexus Mods, or Paradox Mods.
Place mod folder(s) in %AppData%\Surviving Mars\Mods (Create "Mods" folder if it doesn't exist)
https://steamcommunity.com/sharedfiles/filedetails/?id=1777493789 (AppData folder location)
Enable with in-game mod manager