In order to install Android on iPhone you first must jailbreak your iPhone. There are a number of tools you can use to jailbreak your iPhone. For legal reasons, we will not list those tools here.
Once your iPhone has been jailbreaked then install Cydia. In Cydia add the repository, repo.neonkoala.co.uk. Then tap on the repository and install Bootlace.
Then, launch Bootlace in order to patch the kernel. When its done patching it will reboot your iPhone.
Install OpeniBoot from within Bootlace. Simply, launch Bootlace and then tap the OpeniBoot button.
The next step is to download iDroid. You can install iDroid from within OpeniBoot. The iDroid is an android version that is costomized for the iPhone.
If your reading this step and have done everything above successfully, play around with Android. Tap on the Quickboot from within Bootlace and then tap the Android icon. In a few seconds you will be booted into Android.
Now, you can give yourself a pat on the back for a job well done