From Mine Little Pony
You need to download and install LiteLoader to use Mine Little Pony.
Optionally, if you need to use Forge mods too, you must install Minecraft Forge first, before installing LiteLoader. Then chain LiteLoader to Forge when given the option in the LiteLoader installer. Don't select that option if you don't want to use Forge.
Once you have LiteLoader (and any other mods and loaders) installed, download the Mine Little Pony mod.
Place the Mine Little Pony litemod file you downloaded into your Minecraft mods folder.
You must select the "LiteLoader" profile when launching Minecraft.
Read this if you need to know how to install the mod for versions of Minecraft prior to 1.6.
Activating the mod
Now the mod is installed, you will need to change your skin to a special Mine Little Pony compatible skin otherwise you will look like Daring Do. There are some example skins on the download page, and a tutorial about how to create your own skins here.
To change your skin, press "F1" at the main Minecraft menu to use the built-in Mine Little Pony skin manager. Or change your skin on Minecraft.net in the usual way.
Once you have the mod installed, run Minecraft and switch to the third-person view (F5) to see yourself as a pony!
Configuring the mod
Press "F7" when you are in-game to open the configuration menu.
There are a few things you can change about the way Mine Little Pony behaves. For example, there is a setting to allow you to see players who are not using Mine Little Pony skins as humans, and you can change the default pony used by the mod. For full information about how to change the settings see the configuration page.
If things go wrong
If you can't install the mod or if you're having other problems you can hopefully find answers on the support page.