Step 1: Start The Game Once to generate the Mod folderįirst, make sure to start the game at least once. This guide will show you how to quickly and easily add cool stuff to your game with just a few clicks using, a trusted and free Sims modding site since 1999. The Sims 4 has finally arrived on Steam! However, the game is over five years old and as such has TONS of custom content already available.