The shipping bin is the medium that allows the player to sell items from the farm. It is located next to the Player House. The player will be able to see it as he's heading down to Starlet Town. The shipment put into the shipping bin will be sold at end of the day. It is possible for the player to take back items that they put in the shipping bin as long as it's still the same day.
At the end of the day, the money of the sale will be added to the player. If the player wants instant money from the sale they can sell the item to the shop that buys the particular product.