If you are a Gmail user, no worries, you can add contacts, tag contacts, and add notes right from your email.
To Download Levitate Add-on for Gmail, just go to your Email and find the + sign on the right-hand side. Search for Levitate in the pop up, and add it.
Once it's added, Levitate may take a second to appear in the right-hand-side bar. Once you see it, just open up an email and hit the L badge.