It's easy.

1. Face the Mime toward chosen target if it is not a board spell that would be used (like dances and songs)

2. Use a different character to use an ability or an attack the same distance away from your character as the Mime to a chosen target\

ex: M---X C---X M=Mime, C=Character, X=Enemies
Upon the action of the character the mime will immediately use the ability, unless it would miss. __C
M---X---C, _X- , also work and so on.
M--

3. better ways to utilise mimes are to either have many surround one guys and hit it multiple times each attack or use them with dancers/bards/calculators to multiply effectivness.