Documentation:IOS
Preliminary Note
VLC for iOS is different from what you can do with VLC on desktops. In some regards, you can do more, in others, you can do less. VLC for iOS does only do media playback. Active streaming or file / stream to file conversations are not supported for usability and performance reasons.
Media Synchronization
There are multiple ways to synchronize media files to VLC for iOS. Those may be extended in future releases. Streaming without saving files using the limited space available on iOS devices is also supported. See below.
iTunes File Sharing
Using iTunes, you can add and delete files to VLC for iOS. Apple provides excellent documentation for this.
WiFi Upload
If your iOS device and your Mac or PC is on the same local WiFi network, you can use WiFi Upload to add files to VLC for iOS' library.
Within VLC for iOS, click the cone button:
This will expose the sidebar menu. Locate the WiFi Upload menu item. Notice the empty circle indicating the server's off-state and the description "Inactive Server". Note that in earlier versions of VLC for iOS, you'll see a toggle button.
Click the item or switch the toggle. A network address will appear in the item:
Enter the network address to your web browser on your Mac or PC on the same local network:
VLC for iOS' WiFi Uploading page will appear. You can drag any file stored on your Mac or PC to this window for immediate upload to your iOS device. Additionally, you can press the "Upload files" button in the top-right to expose a file selector panel in case your files are not reachable by drag and drop. VLC for iOS' WiFi Uploader supports multiple uploads at the same time and will indicate through a progress when upload is complete. Because it's VLC after all, you can start playback of most files on your iOS device as soon as they appear so you don't need to wait until the upload is finished.