Our purpose is to support owners in their use and maintenance of the Porsche 928 and to foster camaraderie among owners throughout the world.
How to add photos to your Registry entry:
Basically, you need to be in the edit function and select the photo tab.  Let's walk through it:
Next, to the far right of the heading “1986.5 928 S U.S. 1618” you’ll see a print icon, star icon, eyeball icon, and a little gear icon.  The latter is what you want to click, which will initiate a drop-down menu with “Edit” being the first option in the list as shown below.  Select “Edit” and allow the page to reload.
After the page reloads, the heading will now read “Edit Vehicle Information: 1986.5 928 S U.S. 1618” and you’ll see several tabs including Required Vehicle Details, Photos, Optional Vehicle Details, History and Maintenance, etc.  Click on the “Photos” tab.  Here, you’ll be able to edit the “Main Photo” and add or delete “Other Photos”. 
Changing the Main Photo is easy, just click “Browse” and search your computer’s file directory and select the photo you want to use.  Adding Other Photos is somewhat similar, only after selecting you’ll have to “Add Files” – let them show up in a list – then click “Start Upload”.  The upload process will begin and you’ll see the status as each photo file gets uploaded.  Once they’re all uploaded, click “Save and Close” .
That's all there is to it!
Thanks to Jarrod for the write-up.