I started by copying a COBOL helloworld program and working through the concepts on https://www.tutorialspoint.com/cobol
It's very lightweight but that's what I was after.
What I wish I had done from the start was compile with all warnings (-Wall) because it would have caught a few things like me assigning constants to variables (pictures in COBOL) that were not the right size so they were silently truncated at runtime