Making an enemy move can be done using a path. Create several of these and use the 'path finish' events. to make the actor follow a new path and change animation is possible.
The best thing to do, to make something move side to side is to create 2 paths, put a higher integer in 'frame' to make the path longer, and make the actor move swifter. Try to syncronise with the actors animation.
Then click actor control, add event>path finish>change path> path 1 to path 2.
then do add event>path finish 'path 1'>change path>path 2 to path 1.
if you want the animation to change do this:
add event>path finish 'path 1'>change animation 'left.bmp'
and the same for righ or up or down animation. but it will require more paths for that...
Ill let you experiment, ill upload this there image to show key parts.