Here's a step-by-step guide for connecting printers in Prime mobile app.

1. Go to More -> Printer Settings

2. Click on Add New Printer.

3. Prime App will ask you to Turn ON the Bluetooth if not already turned ON, click on Allow.

4. Prime App will ask for Location permission for the first time, click on Allow.

5. App will list all the Paired and nearby Available Bluetooth devices.

6. Click on the Device you want to connect, at this point Prime App will Pair and Connect to the Bluetooth Device.
7. You can also configure the width of your printer for flawless prints.

8. Once done, print a test Bill/KOT and then you're good to go.

The same way you can connect multiple Bluetooth printers to Prime app.

Prime now supports printers that uses Bluetooth v3.0 and above.