If anyone needs it, here's my manual (copy+pasted over)
1. You first need to make a .PNG with all the frames of animation in it. The game divides the .PNG into parts, then displays them one after another, starting at the top left and ending at the bottom right.)
2. Place the .PNG into the following directory: Worlds/My Level/Custom Objects. This way, the game can access the file.
3. Place an object from Bank 255 into the editor in the desired place. Remember the object number, as you'll need it later.
NOTE: If your object is larger or smaller than 24 pixels wide or high, the editor will center it on the Bank 255 object.
4. Somewhere in the level .ini, write: Custom Object X. X is the number of the Bank 255 object you used. Under that, write the specifications for the animations.
Spoiler: .ini Codes (click to show/hide)
*Image= This is where you type in the image name.
Init AnimFrom= This is the image the editor displays first. Default is 0.
*Init AnimTo= This is the image the editor displays last.
Init AnimSpeed= This is the speed the editor displays the images (probably frames per minute)
Init AnimLoopback= When the editor displays the last image, it goes back to this frame. Default is 0.
Init AnimRepeat= The animation loops this number of times. Default is infinite.
Tile Width= The width of the tile. Default is 24.
Tile Height= The height of the tile. Default is 24.
Offset X= How many pixels the animation is moved horizontally. Positive numbers move it right, negative to the left.
Offset Y= How many pixels the animation is moved vertically. Positive numbers move it down, negative moves it up.
*Required
5. Test the level and make sure it works the way you want it to.