In the Zephyr builder, if you see a message that says that a particular area is "Read Only" or if you can't click the "Upload" button, it may mean you are simply in the wrong folder.
You can upload your own images and documents, but first, you'll need to head to the My Files folder.
To reach it, head to the Home page of the file manager and look for the My Files folder name. Click on it, and you should be able to add your images and/or documents. The "Upload" and "Search free photo" options will become opaque and you can click them immediately.