Yes you sell from your house and buy in other seller's homes or from a broker.
To sell, first buy a merchant board from one of the NPC merchants in your home village. (should be 3 or 4 that have them for sale) Then place it on the wall in your room.
Next, put containers in the 2 room vault slots in your roon, (access by right clicking on your door from inside) Now fill the containers and close the boxes.
You can now right click on your merchant board and get a list of everything in your vault. Also the things in your personal inventory. Price the items you want to sell and click the button to list and start selling.
If you want to sell from your room, stay there and the items in your bags as well as those in the vault will all be available for purchase. To sell while you are out adventuring or off line, just leave the room! The goods in your bags will not be available but everything in the vault will stay available for purchase for the next 24 hours.
Happy selling!