Note that the autosplitter only works for the .exe version of ClassiCube, and only for version 1.2.0.

First make sure you have LiveSplit set up, then follow the link to the autosplitter in resources here on the site.

You will be taken to a GitHub Gist containing the script content. Press the "Raw" button, then hit CTRL+S to save the script as a file on your computer. Save it somewhere that you can remember, under the name classicube.asl.

Open up LiveSplit, and go to "Edit layout...". Add the "Scriptable Auto Splitter" component to your layout.

Double click the new layout entry to open its settings. Choose the classicube.asl file you saved for the script path. After a brief load, the "Advanced" section should expand and show you the settings for the autosplitter. Each checkbox indicates whether the autosplitter should split when you touch the given target, so make sure you have e.g. 4 splits in your timer if you run All Borders and have all the border settings checked.

At this point the autosplitter is installed. Note that the autosplitter attaches to the first ClassiCube window that's opened, which usually is the launcher. In order for the autosplitter to work, it needs to attach to the actual game window - to fix this, simply close the launcher window once you've opened the game, so that there is only one ClassiCube window open. You'll know it works if the timer automatically starts after you've generated a new map and start moving.