When you click the Market Stand, the "Sell Your Goods" window will open. Just click on the items you want to sell to get them queued up.

Once they are both selected for sale, just click the ‘Sell’ button and you are done. If you have Ingredients or Crops, you can sell them in the Market Stand for Coins. 

Tip: If you accidentally select something you don’t want to sell, you can cancel the sale by pressing the “X” in the top right of the Market Stand Menu.