I finally got the Steam version of SFS.
I also just wanted to import planet packs...
But in which folder do I put them anyway?
Unfortunately I couldn't find a tutorial for the version on the PC...
Planet packs are not mods, but I suggest that you have a look at this post to know how to access your game files. From the game directory, you'll have to install your planet packs under Spaceflight Simulator_Data/Custom Solar Systems.
