Sometimes we may need players to provide screenshots of the issue they've come across in-game or you may want to share screenshots with the Community - uploading screenshots to Steam is slightly different than you may expect so we wanted to walk you through the process!
Make sure that you have Steam Overlay enabled in your game
Go to Steam > Settings
Click the In-Game tab
Check "Enable Steam Overlay while in-game"
Go to Library
Right-click on the game title and select Properties
Under the General tab, also make sure "Enable Steam Overlay while in-game" is checked
To take a screenshot in-game when using Steam:
Once you are in the game, press F12 to take a screenshot
Then press Shift+Tab to bring up the Steam overlay, and Upload your screenshot - make sure to make it public
Then simply include the URL of your screenshot on the forum (it should look something like "http...sharedfiles/filedetails/?id=...")