To add multiple images, videos, or files at once:
- Go to Library > Files.
- Click the Add Files button in the upper left.
- This will open a pop-up where you can either drag files from your desktop/File Explorer into the pop-up, or click the button to Browse Files, navigate to the files you want to add, and open to add them.
- Once you've added the files you'd like to upload, click the Upload Files button in the lower right.