Thanks for posting! To edit a contact you will want to click into the contact details and then click on any name field. You will see the area open up to make edits.
Hope this helps!
You can add a name to a contact by searching for their email address or finding their email address in your contact list and clicking the contact. From there you can click at the top of the page where you can see First Name Last name to add it in (just like in the screenshot above). Just make sure to click Save.