Installing a new Android build is generally done through your device's recovery mode. The default recovery will only install packages that are signed by the original manufacturer, however, so installing a custom build requires the use of a third-party recovery system. The most popular are generally ClockworkMod and TeamWin Recovery Project (TWRP). The first step to installing a custom build, therefore, is to get a custom recovery. Instructions for this are available on their respective sites.

With a recovery in hand, installing a new build is a fairly straightforward procedure. The following instructions are intended for installing a new update with ClockworkMod on top of one of my previous builds. If you are installing for the first time, you will need to find an alternate manner of booting into your recovery mode, because the menu option may not be available. TWRP users will need to navigate slightly different (but similar) menus.

  1. Download the new build to your device. Storing it on the root of your /sdcard folder is easiest, but anywhere in the /sdcard directory is suitable. Storing it elsewhere is not recommended.
  2. Reboot into recovery mode by holding the power button to bring up the power menu. Select "Reboot" from the first dialog, then "Recovery" from the second dialog. If you use a secure lock screen (PIN, pattern or password) you will need to unlock your device in order to see these options.
  3. Once your phone has rebooted into ClockworkMod Recovery, use the volume buttons to move the cursor to "install zip" and press the power button to select it. Next select "choose zip from /sdcard", then finally navigate to the location of the build and select it. If prompted, confirm that you want to perform the install.
  4. Wait for the installation to finish, then repeat step #3 for the Google Apps package (if you intend to use Google's apps).
  5. Finally, select the "+++go back+++" option until you are at the main menu, then select "reboot device".

Installation can take several minutes due to the size of the system, so don't panic if it seems to take a while on step #3. The initial boot after installing a new build can also be somewhat slow, as Android needs to precompile the new applications.

If your device gets stuck at the boot logo for more than 20 minutes or so, hold down the power button and the volume down button to reboot into your bootloader. Then you can use the power buttons to select "Recovery mode" from the boot menu, and use your recovery system to either flash a different build or try a factory reset to fix the boot issue.