ROM Manager is an app that makes it easy for Android smartphone and tablet users to install custom ROMs on rooted devices with unlocked bootloaders. You can use the free version of the app to flash ClockworkMod Recovery on your device, reboot into recovery, install ROMs, or manage backups.
If you pay a few bucks for ROM Manager Premium you can also download and install a number of custom ROMs including CyanogenMod nightly builds — and now you can also use a new feature that lets you install CyanogenMod simply by clicking a button on a website.
Basically you need to install ROM Manager Premium and enable the Web Connect feature and login with your Google account.
Then you can click the ROM Manager icon next to a ROM at the CyanogenMod downloads page, login with your Google account again, and your phone or tablet should automatically start downloading the software, reboot into recovery, and install it.
You can also still install ROMs manually by downloading them from the website, copying them to your device, rebooting into recovery, installing the update, wiping your cache, and so on. But the CyanogenMod/ROM Manager Web Connect feature makes the whole process a lot simpler.
via Android Police