You can click 'manage display' to put items on the window once you have it placed to put things out for sale. You may also use this as extra storage for your inventory. Some items will cost a storage tax to sell. The bigger the stack of items put of for sale the more the storage tax is. If it is a stack of one item it is possible to put it on sale for one or two kamas without being charged the storage tax, though the prices can vary depending on the taxes set by the governor in each territory. Items put on display for extra inventory storage and at 0 kama will have no storage tax, but can be bought by other players.