Well first of all you would have to make the enemy movement. If you've made it yourself you'll get better control.
Then to make it act randomly you need to ask MMF2 for a random number. with say...
set value to Random (10)
which would choose a number from 0 to 9, or
then you can make an event starting with the qualifier
value = 0? do this
value = 1? do something else
value = 2? do a third thing
etc
the value can be anything really, a global value? or an alterable value from an active object or even a counter.
If you want the character to shoot in a random direction, just select them all and it will shoot in one of those directions at random.
Otherwise use the trick with random and comparing values for what to shoot (or in which direction, but the direction thingy I mentioned above is easier for that).