There are two ways you reach the redemption window for your Featured Game Ticket.
—To get to the redemption popup window, either click on the Featured Game Ticket in your inventory, or on the splash page of certain games, you will see a message that says "You have a featured game ticket that can be redeemed on this game. Click here to do so." and by clicking that, you will bring up the redemption popup window as well. This will use up your ticket and it will disappear from your inventory.
—From there you select the action to "redeem ticket" and you will see a drop down menu with all the available games. When you select the game you wish to set as the Featured Game, click on "Set Featured Game" and that will be your new Featured Game for the next 24 hours.
Just a suggestion, please be aware to not choose a game that you have already submitted scores for, for that day. If you choose Meerca Chase II and you already had played it 3 times today, you will not have any plays left to take advantage of your Featured Game Ticket for today.