[HI there, you’ve posted here and sent us an email, so we’ve been working with you on email.]
The short of it is that there are several steps. The first thing you need to do is open the MIDI Designer layout (the .mididesigner file) on your iPad and use “Open In...” in your browser to open it in MIDI Designer Pro 2.
Then you need to be able to send MIDI from MIDI Designer to Ableton Live via musicIO MIDI, the built-in connection over Lightning Cable, or MIDI over Wifi (check midiDesigner.com/connect, which is outdated but still relevant).