Set Up an Email Signature in Gmail

To set up a digital signature automatically  to emails you compose in Gmail

STEP 1:
Click the Settings gear button in your Gmail inbox toolbar.

STEP 2:
Select Settings from the menu-bar that will have appeared.
STEP 3:
 under that select General.
STEP 4:
Go to Signature under that select signature radio button

make sure the desired account is selected under Signature.
STEP 5:
Type your  signature in that signature text field.
it allows you to add your signature and signature image.to add image select insert image button on formatting bar.It's best way  to keep your Gmail signature to about five lines of text.
STEP 6:
Click Save Changes.

Gmail will now insert the signature automatically when you compose your  message.