- Make item (e.g. A sword). (Items>weapons>New)
- Make a container. (WorldObjects>Container>New)
. Drag your sword into the inventory of the container.
- Make a faction. (Character>Faction>New)
. Set up the faction as a vendor (Vendor Tab in Edit Faction)
.. Set the vendor to use your custom container.
... Set the vendor to use a vendor list e.g. VendorBlacksmith.
- Create an NPC and in the faction tab select your faction (RightClick>New>YourFaction)
Make sure JobMerchant and/or Jobblacksmith factions are in the faction list for the NPC or your NPC will not sell you anything.
Baratan made a useful totorial video showing you how to make a copy of an existing NPC and make him a new vendor.
http://www.youtube.com/watch?v=XoRcimDR8fY