You can upload files from your mobile device to Sync. Here's how:
1. Open the Sync app
2. Tap the + button (bottom-right corner of the screen)
3. Select Upload
4. Tap Menu (3 horizontal lines from the top-left corner of the screen)
5. Navigate to where your file is located
6. Tap the file you wish to upload (you will get a prompt that the file is being uploaded)