Try "man tmux" 
Where the version on Elive use "Ctrl a" and not "Ctrl b" .... once a tmux instance is opened type "help" for more or read the ".tmux.conf" file in your home directory.
So on Elive "Ctrl a" followed by "|" (pipe symbol) and if it drives you mad:
Type "exit" and Enter to disconnect. 
and ...
"Ctrl a" and "?" to list all key-bindings.
