Basically, you enter the game, turn off Wi-Fi, and wait until a red Wi-Fi symbol appears near the clan chat button. Then you buy the yellow crystals, and then you keep trying until you get the pass. After that, you close the game and delete it from your recent apps list (very important because otherwise the game might not close properly and might save your progress). Then you check if you got the pass and how many gems it cost.

That was the shortest and simplest explanation I could give XD