Note: Make sure you are using either Google Chrome or Firefox during the installation process.
Salesforce allows only 1333 characters in the signature section, so make sure your signature is neat and not bulky.
After you finish creating your email signature, click “Save and Install” button under the signature preview:
Or if you have saved your signature priorly, hover over your signature on the dashboard and click “Use” button. Choose the way you want to install the signature on the pop-up window:
Select the option Other in the list of email clients.
Select the HTML tab, scroll down the Signature code and Click the “Copy and Proceed” button, which will save the signature code in the clipboard.
Open Salesforce and go to your profile Settings:
Scroll down to My Email Settings.
Select the to Send Through Salesforce and Paste the code into the placeholder:
Save the changes and check your new signature by sending a test email.
Congratulations! Now you will see your new signature in every email you send with Salesforce.