From the Raptr website, click on the Profile Picture on the top right of the page and then click on “Manually track games”.

It will reveal a list that has all of the games in your library. 

You select the game through the drop-down menu and then select the amount of hours and minutes you had played the game. 

For the duration of this play session, you will be seen on Raptr as playing this game. Once the session ends, your status will change back to normal and the game time will be added to your account.