Not sure which you're selling exactly, or what question was...
If you want to sell one of the trailers, click on Classifieds tab at top, and follow steps to list it there. Folks can search on it.. Be sure and list multiple means of contact (some people insist on telephone to talk live), the location of trailer and price or other details you would want to know as prospective shopper..
As for pictures, they will make or break selling, and if large and computer on phone line, just shrink photo's to more manageable size... Use "edit" and "resize" commands in photo editor to get picture size down to around 600 x 600 pixels, and then upload 2 or 3 at least...
You can look at other units for sale in classifieds (vintage trailer section) to get ideas on pricing, or check vintage airstream club website on values. If you don't get real good information, try listing at slightly higher price, and wait for buyers to tell you why your price is too high, or get on plane to write a check...