Just open your storage and press on the resource you would like to exchange for experience stars. You will see the icon with a star below. Tap on this icon if you want to exchange one object or hold if you would like to exchange several. This feature will be helpful if you would like to advance in the game faster or to empty your storage.


Note: All items from the "RARE" section don't take place in storage and can't be exchanged for experience. You don't need to worry about their quantity.