You can download the iOS version from the App Store. The Android version is available in Google Play. You may use any Apple or Android device as long as the Apple devices are running an up-to-date version of iOS, and the Android devices are running an up-to-date version of Android.
Once you have installed the app, you will be asked to scan a QR code so that your external device can communicate with your Clover. To obtain the QR code, launch the app from your Clover device, and a QR code with your Merchant ID will appear on the main page. Click on the code, and it will print from your receipt printer.