You can earn these resources (sometimes referred to as RSS) by harvesting from your own lumber mill and sheep farm. You can also earn additional resources by attacking other players and stealing from their lumber mills and farms! Lastly, you can request Food and Lumber transfers from your teammates. You will receive it automatically in your storage after 10-20 minutes. Make sure you have enough room to hold it all!
When you destroy lumber mills and farms, you will find how much you earned after you have defeated your enemy. Don't forget, joining attacks and inviting team members to help you out can result in higher food and lumber rewards after defeating your enemy.