There lots of info available about using arecord:
However a quick getting started would be to install hexdump (to allow you to take a peek at the audio as text):
apt update && apt install bsdmaintools
Then run a simple pipeline to convert the incoming audio into text:
arecord -Dhw:DB410c,2 -f S16_LE -c 1 -r 48000 | hexdump | head
The result for me (with no audio routings set up because I have nothing attached to my board) is a bunch of values that settle close to 0 (i.e. quiet white noise) which is what I would expect:
0004820 0003 0006 fffc 0002 0004 ffff 0003 0006
Note that the numbers starting ff are actually close to zero (this is how small negative numbers are represented).
You'll know when you get the audio routing correct because the numbers will start to get much more variable!