To use a Fire TV Smartphone app, you’ll need access to a separate device. Any Android phone or tablet will work, as will iOS hardware like iPad's and iPhone's. If you have a fourth generation Fire Tablet you can even use the app from there! Search your devices app marketplace for a compatible remote app. Amazon has an official one called Amazon Fire TV Remote App, and it’s by far the best software for the job. There are also plenty of third party apps you can use for voice control and basic Fire TV navigation.
Once you have the remote app installed, it’s time to pair it to your Fire Stick. Make sure the Fire device is turned on and connected to your home Wi-Fi network. Next, turn on your phone or tablet’s Wi-Fi and connect it to the exact same network. Launch the remote app, then select the device you want to pair it with. You may need to sign into your Amazon account before the device can be located. A code will then appear on your TV. Enter that into the app to confirm the pairing.
Whenever you open the app and have your Fire device active, you should be able to control it with your phone. If problems arise, make sure both devices are using the exact same Wi-Fi network, or try rebooting the Fire TV.