How do u make units shoot units?

In the editor upgrade i downloaded it says you can make units shoot units. I have typed many strings under attack that could cause them to shoot a units but it doesn't. So plz help me with this.

You have to type the path, and have it have a .mdl extension. For example:

To make a unit shoot footmen, use Units\Human\Footman\Footman.mdl .

thx