How to install signature in iPhone?

1) Send an email to yourself from your computer or device that already has HTML signatures set up on it. It can be just a blank email with your signature.
2) Open the email in the Mail app on your iPad or iPhone.
3) Press and hold down on the signature in order to bring up the selection tool. Move the anchors so that you have the entire signature highlighted.
4) Tap on Copy.
5) Press the Home button to return to your Home screen.
6) Launch the Settings app.
7) Tap on Mail, Contacts, Calendars.
8) Tap on Signature under the Mail section.
9) Tap on the account you would like to add the signature to if you have signatures set up per account.
10) Tap in the signature field to bring up the selection tool again.
11) Tap Paste in the popup menu.

NOTE: The signature formatting will look incorrect. Do not worry, we will fix that in the next step.

>> Your device will tries to “enhance” the signature when you paste it by default, making your signature design look all messed up and distorted. Luckily, they allow us to Undo these “enhancements”. Shake your device (iphone/ipad) until an “Undo Change Attributes” screen shows up. Then click on “UNDO”.

>> Now you should see your new signature when you compose a new message on your iPhone/iPad/iPod.