To quickly add a contact, select the +Add button, located at the top right side of the page and click Contact, as shown below.
The dialog box appears where you will enter the Contact's Name, the Company they are affiliated with, and their Address (as highlighted below). Click Save to commit your changes.
You can also add a contact from the Account Profile Page by clicking on the +Add button on the top right of the page to add a contact.
One of the advantages of creating a Contact from the Account page is that the Company field is auto-populated, leaving only the Name, and email to be populated prior to saving.