Add a contact to Salesforce

You can see the Salesforce Sidebar if you're on the  Growth or Enterprise plan. Click the blue button in the top right corner to expand the sidebar: 

If you're viewing an email from a person for whom you have a record in Salesforce, you can see and edit their record in the sidebar. If there is no record associated with that email address, you can create a record:

Simply click on Create Contact or Create Lead to add the contact into Salesforce. Check out this video for more detailed instructions: