Click “Next” and follow the prompts to complete the setup process.
Enter the Steam key you received from the seller.
Click “Next” and accept the user agreement.
Click on the “Add a game” icon (plus icon) on the bottom left.
To add the game to Steam and unlock all of Steam’s perks, here’s what you need to do: If you’re using a different platform to purchase Steam games, such as GOG or Humble Bundle, you’ll usually get a Steam game key once you complete the purchase. You’ll still have to access the native client(s) to download updates. You have to keep in mind that adding a non-Steam game in this manner doesn’t allow Steam to update the game in the future.
Once you add a non-Steam game this way, you can open it directly from the Library menu or the toolbar shortcut.
Select “Add Selected Programs” to finish the process.
If your game isn’t on the list, use the “Browse” button to open the location manager and find the game’s. Select your game’s name to add it as a non-Steam game.
Steam will generate a list of all available programs and executables found on your PC.
Select “Add a Non-Steam Game” from the list.
Click on the plus icon (“Add a game”) on the bottom left.
Steam allows any game, regardless of its publisher or presence on the Steam store, to load from the platform as a non-native game. There is another method that will enable gamers to play their favorite titles through Steam.