To complete an order and earn stars/golden tickets, you need to create the requested items by merging.

You can always check the related item chain by tapping on the item itself in the order. The orders will have a green checkmark on them once you prepare every requested item. Tap the checkmark button to complete your order and earn stars/golden tickets.

If you want to see all your current orders, you can always scroll left and check them.

There is another indicator on both your order and the game board for the order status. Seeing a green base behind an order means you already have it somewhere on your board.

If you see a tiny green checkmark on the bottom-left corner of an item, it means that this item is requested by one of your customer orders.