how to install win8 on mountain lion 10.8.2

Installing Windows 8 is not worth doing because Apple has not released compatible drivers for it. As for when that will happen, remember it took 3 months to get drivers for Windows 7.

If you would like to have a go installing Windows 8 onto Bootcamp before Apple release the official drivers, you can follow the detailed instructions on this Ars Technica article here.