HI All,
Would like to recommend you the use of byobu (instead of tmux).
Byobu is installed as part of the image (and if not it is easy to install)
I found it much more user friendly and working perfectly during a ssh sessions.
It uses tmux as its engine but doing a better job in user interface and keys combination.
For me that tmux did not work as expected.
The prefix-key combination was working only partial of the time, and also it caused my ssh session to terminate.
you can find an easy tutorial at at: Byobu tutorial
Good Luck!