You can sell items in the Marketplace. Other players, James, and even Peter Panda will visit your Marketplace to purchase them.
Click on the Marketplace to open the Marketplace Menu. Select a basket with a New Sale sign to put an item up for sale.
Choose an item you'd like to sell from your inventory. Tap on it, then use the plus and minus symbols to choose the quantity. The amount of coins you'll earn will appear under the item's picture. Click on the Sell button when you're ready to sell those items; once the Sell button has been clicked, the items cannot be recovered.
Once someone else has purchased your items, coins will appear in the basket. Tap on the basket to collect the coins.