Tap a locked building to see a list of items you need to unlock it, as well as how many of the items you already have. If you tap on the magnifying glass in the top right corner of an item's icon, the game will automatically bring you to a building where you can get those items. Win levels in these buildings to receive the items you are missing. Please note that, when you successfully complete a level, you may receive one of the three items shown at the beginning of that level. You will not always receive the exact item you need at that moment. The game randomly determines which item you receive for completing a level, even if it is an item you do not currently need.