To use any official autosplitter, set your game in LiveSplit to the same name as found on speedrun.com. Then click on "Activate".
Alternatively, you can download the latest .asl file. Then add a Scriptable Auto Splitter to your layout. In the Autosplitter's options, browse for this file and choose which settings you want.
You can access the following autosplitters directly from Livesplit, no need to download anything.
These are the autosplitters I didn't publish officially, either because they're buggy, I'm still working on it, or a modification of an official one.