The Order Board is located near the left side of your farm. Tap on the Order Board to open it and see the Orders.
Each Order shows how many Coins and how much XP you'll receive for completing it.
Tap the Order and the need Goods appear on the right. There are numbers under each required item. The number on the left shows how many of that item you have. The number on the right is how many you need to complete the order.
A green checkmark means that you have all the Goods needed to complete that Order.
Tap the Deliver button to complete the Order. Wait for the Truck returns and tap it to collect your reward. In addition to Coins and XP, completing Orders can sometimes give you bonus rewards, such as Materials.
If you don’t want to complete an Order, tap on the trash can icon on the right. The new Order will take its place after few minutes. You can replace it instantly for rubies.