my Apple TV

Some things to try:

Make sure that your Apple TV and and your iOS device are on the same Wi-Fi network.

1. Restart your device. (Phone)
2. Close the Remote app and then re-open and try again. To do this, double press the Home button (if your device has a Home Button), if your device does not have a Home Button, e.g., iPhone X; swipe up and pause, then find the Apple TV Remote app, and swipe it up. Now relaunch the app.
3. Unplug Apple TV from the power outlet for 30 seconds, then plug back in.
4. Make sure that your iOS device has the latest version of the iOS software. You can update your device by going to Settings > General > Software Update. 
5. Restart your Wi-Fi router by unplugging it from the power outlet for a minute and plug back in.

If you have an older Apple TV then a physical remote would be required to pair with the remote app. You can purchase a replacement from Apple

An alternative would be if you had a Bluetooth keyboard. However, you would need to restore the Apple TV via iTunes and then pair with that during the setup process. There is also the cider TV app, but it requires a Mac and also needs the Apple TV to be restored prior to pairing.