There are two animation editors available in Essentials. The first is the default RPG Maker XP one, which is the Animations tab in the Database (F9), and is used to make field animations (grass rustling and so forth). That's not the one you want here. The animation editor you want to use for battle animations is the one made specifically for Essentials. It is found either in the Debug menu in-game or in the External Editor. This is referred to as the Animation Editor (with capital letters).