There are many types of wagon, container and vehicle in Avalon and each distinct type requires slightly different treatment. See HELP WAGONS for info on using wagons and carts, HELP CONTAINERS for details on the employment of containers (generally for liquid or smaller-scale transporting of goods), and finally HELP VEHICLES for insight into how to use the larger vehicles - like trading caravans - to transport goods about the land.
Syntax: UNLOAD <item> FROM <container/wagon/vehicle>
When unloading from containers or wagons, you will typically need to be standing in the location outside - leading the wagon or holding the container (or at least having it close-to-hand). The unloading process will carry on automatically until you CEASE/STOP it. Unloading from vehicles, however, requires the large transporter to be open (i..e. its doors not locked up shut) and for the person doing the unloading to be inside the vehicle when the UNLOAD command is issued. He or she must remain within the vehicle until the unloading is complete.
Syntax: LOAD <commodity> INTO <vehicle>.
This command is used to place commodities from your inventory or from the location floor, into an open vehicle (i..e. whose doors have not been locked shut). The loading is an automatic process and continues 'til you have completed the task or type CEASE/STOP.