Step 0: Check if screen is installed
screen
If not run
sudo apt -y install screen
Step 1: Create a screen session with a meaningful session name
screen -S sessionname
Step 2: Check if you are in a screen session
$ echo $STY
If the result is something like this:
941609.sessionname
you are currently in a session.
Step 3: Exit and terminate screen session
$ exit
Step 4: Exit and keep screen session running (detach)
$ screen -d
Step 5: See existing screen sessions
$ screen -ls
Step 6: Reattach to existing screen sessions
$ screen -r sessionname