Thanks for the question. I understand you wish to add a contact from Mail. The following article outlines how to do so:
In an address field of a message you’re sending or a message you received, move the pointer over an address, click the arrow that appears, then choose Add to Contacts.
In a message you received, move the pointer over a phone number, email address, or street address anywhere in the text. Mail outlines the information; click the arrow and choose an option from the pop-up menu. For example, add the data to an existing contact.