I think the only part where I can be of help here is by telling you how to have the Bela cape show up as an ALSA device, but for the rest of the setup, it is for you to follow the instructions made available by
Now, the "Bela as ALSA" issue. I rarely do that, so it periodically breaks. After about one hour of work on this, I got got it to work for Bela, but it is still not doing it for BelaMini. Before going through this more in detail, which one do you have at the moment? If you have a two big Belas around, it may be easier for me to tell you how to do it there, then you try to get the sonobus to work on those two and evaluate if that works for your purposes, at which point I'd look into fixing this for BelaMini, too.