not sure what your game looks like.
you can spawn an enemy to a position (or a random position) of your choosing (i use spawn-ers)
are you doing it in a single straight line vertical or horizontal layout?
if vertical you could just spawn the enemy at the top of the level, and let it fall, with add input left or right depending on where the player is. Then on contact, destroy it/ - score, or whatever you want
if horizontal layout: you could have the enemy simulate a jump if the player Y > than the enemy y.
this works if the player has the platform behavior, give the enemy the platform behavior but cancel the keyboard input on its behavior settings
(don't forget to add a for each enemy (possibly is on screen) event so it affects a single enemy not all of them.
also destroy the enemy when it fall behind the player by a set amount