I. Before You Begin
1. You MUST be rooted and have a custom recovery image (you can find your rooting procedure for your phone here) and you must have Android 2.2 on your device (load a custom Android 2.2 ROM on your phone after rooting if you have to).
2. Please keep in mind that the new multitouch feature (holding down shift or alt and touching another letter) will not work until you have the Android 2.3 ROM on your phone because of missing framework.
II. Flash the Keyboard
1. Download the keyboard .zip file and save it to your computer.
2. Plug your phone in via USB cable and mount the sd card so you can transfer files to it.
3. Copy the keyboard .zip file (do NOT extract it) to the root of your sd card (NOT in any folders, just on the sd card itself).
4. Unplug your phone.
5. Boot into recovery mode (same way you flash a custom ROM).
6. Click on Nandroid and make a backup (just in case).
7. Click on Flash .zip from SD card and choose the keyboard .zip file and wait for it to finish.
8. Once it is done, hit reboot system now.
III. Select the Keyboard in Android
1. Find an input box (open messaging for instance).
2. Hold down on an input box (like where you compose the message) and select Android Keyboard. Done!