If you're refering to Final Fantasy Crystal Chronicles Echoes of Time, the scratch cards can be used at Mog's station at the town, on the entrance to the left, from where you enter. Each type of scratch card has a different puzzle to take a chance on, the most common is the scratch all the squares in a minute (at least in my one). On the flip side of the card, there is a power (eg, all party members can double jump), if the scratch card is won, then you can use it. (hint: try the cactuar on the world map) most card are either recieved from enemies, or special places that magic will release. when you finish the game there is a secret character that, to make him join your team, wants to see your rare scratch card collection.