When looking at using the Classic interface, it's useful to know the essentials of the Classic interface command structure. That starts with the notion of Major and minor commands.
All Classic product provided screen spaces are composed of these Major and minor commands. In the example, on the top portion of the screen shot, we see the Major command, ALLJ (for all jobs), and three minor commands, cpu, dprt, and ecsa. Think of it as the minor commands provide detail for the corresponding Major command. Also, notice that the Major commands are in ALL CAPS. The minor commands are all in lower case.
Not familiar with all the commands? You can break down and read the manuals. But, you can also use some classic commands to list the Major commands. For example, you can do H.MJC to list the Major commands, and provide a one line help for each. I show an example of this in the screen shot.
Don't know all the minor commands for a Major? No problem, just execute .EXM underneath a given Major command, and it will execute the minor commands for a given Major (as I show in the example).
Knowing how to get the commands is a great starting point for what we will be discussing next.