It is easy. Just post some photos of the inside and outside of the van in this section of the forum. Provide a description of the van, price, mechanical condition, etc. Take a look at other posting in this section to get some ideas of what to include. Most important is the price you are asking and the location (city and state) of the van.
, will tell you how to post photos.
Good luck with the sale and finding a complete rig.