The mode for editing mixal source files is inherited from fundamental-mode, meaning that all your favorite editing operations will still work. If you want a short introduction to Emacs, type C-h t inside Emacs to start the tutorial.
Mixal mode adds font locking. If you do not have font locking globally enabled, you can turn it on for mixal-mode by placing the following line in your .emacs file:
(add-hook 'mixal-mode-hook 'turn-on-font-lock)
You can also customize the colors used to colour your mixal code by changing the requisite faces. This is the list of faces used by mixal-mode: