If you want to use one of the items you have in your barn, just visit one of the production buildings you have in your farm and start producing new products for which that item is requested. You will be able to produce products if you have all of the requested ingredients (just tap on the product icon to see what you have available and what not).
You can also sell the items you don’t need in your roadside shop. Just tap on your roadside shop, tap on an empty crate and fill it with the item you want to sell.
If you need more information, you can also check our FAQ section at our official Facebook page ( https://www.facebook.com/HayDayOfficial) or you can visit our forums ( http://forum.supercell.net/). We have many experienced players there and they can help you through the game! 🙂