To change a unit animation in the object editor.. follow these steps...
1) Open your map and go to the object editor, then to the abilities tab.
2) Create a new ability based off of "Unit-Lightning Attack" and name it Attack1, Click OK.
3)At the very top of your new ability there's a slot named "Art-Animation Names" Open this and modify it to your unit's amimation. I.E. If I wanted the Blood Mage to use only his first attack animation ( select the units model file and labeled in the little box above the WEV[world editor viewer] it says "stand", click on the arrow keys to change which animation you want to view. I'm going to use the "Attack" amimation for this one. NOT "Attack-1")
4) Set the animation in the boxes, if the animation has more than one word they are separated by commas ",".Click OK
-NOTE: animations can be difficult and a really hard one can result in some complications.. try using as many close strings as possible and if they don't work try a different variation(variation meaning instead of "attack,1"-"attack,one" not something like"strike,1")
5)Make sure that all lightning, missle, and target information as well as graphics are cleared.
6)set the target(s) of the ability to what you want to hit with and you're done ^_^(give the unit(s) the ability of course)