To purchase the tickets for Candy Crush Saga using Facebook credits make sure you are logged in to your Facebook account and have the app loaded on your device. When you get to the promt where you are told you need ticket, select the option to purchase them. A screen will pop up asking how you wish to pay. Select "Facebok Credits" and confirm the purchase. You will see a confirmation screen. If you are using multiple devices like me you might still see the screen asking you to purchase the tickets or ask friends for them. Click off of that window and it will recognize that you have the tickets needed to go to the next level.
When I used Facebook to load the game on my laptop I got a ton of extra accomplishment rewards but they were not reflected on the game I had on my tablet. I needed to close out the program on the tablet and restart it to see the perks. One of the best perks was bumping up from three maximum lives to five maximum lives. That comes in extremely handy when you aren't playing for a couple hours and your lives replenish.
Now that I know that I have a 'good' use for the Facebook credits I am going to keep redeeming the caps when the promotions are going on. There are other ways to earn Facebook credits; take surveys, complete site events and redeem them from purchased gift cards. While I hate spending 'money' on games and apps, if I can use credits that I got for free then I will keep on playing!