Here's a GREAT little application to help you export your Tray files for others to share, OR to even download files from the Gallery in the same manner.
http://luniversims.com/files/file/73-si ... -importer/
You must be registered at L'universims in order to download the file.
It's clean, and doesn't cause any problems with your computer. I believe this newest version is compatible with Windows 7, 8, and 10. There's also a beta version for XP. Plus they also have a Mac version (in a different directory).
Anyway...there are installation instructions on the download page (which is in French, with English translations below the French lines of text).
It's very easy to figure out.