Click your Settings icon (the gear symbol at the top right of your email page) and click on SETTINGS in the list.
Being sure you're on the GENERAL tab, scroll down the page to the SIGNATURE box.Place your cursor where you want the logo to appear.
Looking at the menu at the top, find the 'INSERT IMAGE' icon and click.
This will bring up a window 'ADD AN IMAGE'
Looking at the menu at the top, click on 'Web Address URL'.Copy and paste the following into the "PASTE AN IMAGE URL HERE'box:
Click 'Select' and it should appear in your signature box
If you want to re-size the icon you can click on it and choose 'small, medium or large or original size.This is also where you can remove the icon.