I agree that you point at a monster and say "this guy will act now", then play Dash followed by a move action and then an additional move action.
In order to receive the additional move action that Dash provides, you must perform a regular move action first.
Example1:
If the Overlord doesn't want to move a monster could he play Dash?
Well he could, but he wouldn't receive the benefit from it because his monster has to move in order to receive an additional move action.
Example2:
What would it take to double move to reach a space where the monster could attack from and then attack?
The Overlord would have to say "this guy will move now", then play Dash followed by a move action and then receive an addition move action. This is the first action.
Then the Overlord would point to the same monster and say "this guy will attack now", then the monster would perform an attack action. This is the second action.
In order to receive the additional move action that Dash provides, you must perform a regular move action first.
Example1:
If the Overlord doesn't want to move a monster could he play Dash?
Well he could, but he wouldn't receive the benefit from it because his monster has to move in order to receive an additional move action.
Example2:
What would it take to double move to reach a space where the monster could attack from and then attack?
The Overlord would have to say "this guy will move now", then play Dash followed by a move action and then receive an addition move action. This is the first action.
Then the Overlord would point to the same monster and say "this guy will attack now", then the monster would perform an attack action. This is the second action.