1 channel = monoMy BRSTM file is indeed 0 Bytes. I don't really know what means 2ch (2 channel i would guess but still don't know what it is nor how to change it), however my input file was a 44100 Hz FLAC file. i'll try with the song you linked me and edit that post.
2 channels = stereo
4+ channels = surround
To convert a mono audio file to stereo, import the same track twice, then click on the drop-down menu of the first track (next to the "X") and select "Make Stereo Track".
Make sure the "Project Rate" is 44100 Hz, then export it as FLAC.