Hey! I'll try to make this as simple as possible as this game can become pretty complicated.
There are two versions of the game: Vanilla and Loader. To use the different positions feature, you need the Loader version of the game + a mod called animtools + a txt file for the position.
The easiest way to get them all together in a nice package (along with a bunch of other great mods) is to download Sby's Loader Pack 4 from the official game forum: stdmods.com
Or just follow this link, download the file and unzip it.
Let me know if you want to go further with this. I'm happy to help out, but I don't want to type out the instructions if you're not interested.
Cheers!