First make some new sprites (the more sprites the more complicated the animation) You also can use the g_monster sprite as the base if you are not animating the torso
Just cut out pieces of your monster and paste them into these new sprites
Then make a forever and in it is "goto g_monster" and below that is some "change y" and "change x" blocks to put it in the right position.
And after that... Well Make it animate! Just make sure it is in another forever! and bam! You are done! It even works with dodging!