When using non-Shipping builds, or with External Start enabled for Shipping builds, a receiver is registered to allow remote start and stop of the file server. You can then use the UnrealAndroidFileTool to connect to your device's file server and manage files. Otherwise, with AFS enabled, you need to start the file server manually from inside your Unreal Engine application. Refer to Manually Starting and Stopping AFS with Blueprints for more information.