Original Article: http://mcupdater.com/doku.php?id=installation These instructions are for MCUpdater 2.0. Quite a few things have changed since then, and updates are forthcoming. For more help, see us on IRC.
Please note. MCUpdater tries to muck with the Minecraft jar as little as possible. Old (pre 1.36) versions of MCU would constantly overwrite everything in the .minecraft folder, but newer versions store their data in a parallel .MCUpdater directory and launch your selected instance from there.