At this stage, your keyboard should be detected automatically.
Then connect the adapter’s Micro USB end to the Android device.
Take the cable that you have connected to the keyboard and to the OTG USB A to Micro USB adapter or OTG USB C to Micro USB adapter depending on your device.
You should connect the MIDI end of the cable to the keyboard. If the keyboard has a MIDI port, you will need an OTG adapter or a MIDI to USB cable. You should connect the end of USB B to the keyboard’s “ TO HOST” port.
If your keyboard has a USB to HOST port, then you will require a USB TYPE A to USB TYPE B cable.