How do I get keys?

When you reach a gate or barrier with locks you need keys.

You can play for keys, which means just play through 3 levels to get them but the game restricts you to playing 1 level every 4 hours. If you are in a hurry you can either ask for keys from facebook friends if you have used the log in with facebook option and you have friends who play the game. Or you can buy the keys with in game coins. They cost 70 coins each.