There are two ways of connecting this app with your PC:
1. Wired (Connecting through USB)
You need to set on your smartphone type of USB connection to MIDI. In some versions of Android it is unfortunately necessary to turn on developer mode first – otherwise, when connecting, you should have listed all connection types, including MIDI. Then, restart app and you should see your MIDI port in "Outputs" and "Inputs" selects above.
2. Wireless (Connecting through WebRTC)
Learn more at WebMIDI Receiver
After connecting input/output MIDI port, you should be able to use basic MIDI modules (piano, chord maker, arpeggiator, drum pads) without any additional settings. Other functions (console and timeline control in top-right corner of this app) need your DAW to be set properly with Control Surfaces. If Control Surfaces are supported in your software, you could use "Learn" mode to assign MIDI commands from this app to your DAW.
If you have any problem with properly running this app and connecting it with your DAW (Digital Audio Workstation), let me know via any of the contact methods listed there: https://krylan.ovh/portfolio/en/contact
(Of course, it's not only for DAWs, but for any software which receives MIDI input – it can be used even as keyboard for Synthesia :D)