Okay. The first line of code was magical. It brought up a window with a piano keyboard.
I figured out to make it disappear with a " ctrl-c "
I am SO close now.
...
I moved "niju.rom" to the "bin" folder ( because "piano.rom" was there… )
and finally figured out how to copy the path to the file.
I reworked the code phrase and ran it in Terminal:
./uxnemu ~/Users/*************/uxn/bin/niju.rom
But I get this message : " zsh: no such file or directory: ./uxnemu "
Thx again for helping me.