Half a dozen commands will get you 90% of the way there. After you've run tmux:

  ctrl+b followed by...
  % - split pane vertically
  " - split pane horizontally
  arrow keys - change pane you're typing in
  :new-window
  2 - switch to window 2
  x - kill pane
  d - detach

Command line arguments:

  tmux list-sessions
  tmux attach #will attach to last session by default
  tmux attach -t0 #will attach to session 0