Install and open Files To Other Devices on both Android devices. Connect them to the same local Wi-Fi network. Internet access is not required for the local file transfer, but both phones must have access to a Wi-Fi network that permits communication between connected devices.
If you are using a guest, hotel, school or workplace network, its isolation or firewall settings may prevent the phones from finding or connecting to each other. Try a trusted home network where device-to-device communication is allowed.
For this application, the shared Wi-Fi network is a prerequisite for the devices to connect. After connection, file copying uses Wi-Fi P2P. The general ability of Wi-Fi Direct to work without a router does not mean this app has been tested without its required shared Wi-Fi network.
Choose the photos, videos, documents or other files you want to send in the app, then start the transfer. Keep both phones nearby, powered on and connected until completion. The time needed depends on the number and size of files, device performance and wireless conditions.
On the receiving phone, check its Download folder and any destination folder selected in the app's settings. Open a transferred photo or document to confirm that it arrived correctly. Keep the originals on the sending device until you have verified the copies.
Confirm that both phones are on the same network, that the app is installed and running on both, and that the network does not isolate clients or block required device-to-device traffic. See the troubleshooting guide for a systematic checklist.