From: https://www.cyberciti.biz/tips/connect-soekris-single-board-computer-using-minicom.html

Also: https://www.cyberciti.biz/faq/find-out-linux-serial-ports-with-setserial/

To check for ttyS0 settings

demsg | grep tty
setserial -g /dev/ttyS[0123]

Settings
minicon -s

for help 
Ctrl-a ... Z

From: http://linux.die.net/man/1/minicom From: https://help.ubuntu.com/community/Minicom

Using the program
In order to find the name of your port(s) enter this command in terminal:

dmesg | grep tty

sudo minicom -s