Items can be sold to other players in the game by opening a Personal Booth.
To do this, go to the Menu button in the bottom left corner of the screen, and select "Booth" then "Open Booth".
A new window will pop up and allow you to set up your booth. In this window, you can add a name to the booth, stock your booth with items from your inventory, and price the items. When finished, select "Open Booth;" this will allow other players to see and shop at your booth.