A professional email signature has all the contact information making it super easy for the recipient to call you and quickly open your website/Facebook page/blog. (You are also required to have the proper signature in every email you send.)
Open your email.
Click the gear icon in the upper right corner of the screen.
Scroll down the page.
Select the button below the No signature button.
Leave a space before your signature. (Like the yellow highlighted section.)
Add your signature.
Building and address
Phone Number and Extension
Links (blog, Facebook...)
Scroll down and click save!