How do I copy a friend's Facebook profile picture to my Google Contact entry for my friend?
Download the photo. On the website, you achieve this by clicking "Options" at the bottom of the photo, then "Download".
Upload the photo as the contact's profile photo. On contacts.google.com, you can achieve this by going to the contact, then clicking the pencil icon (which means 'edit'), then clicking on the grey profile icon on the left. The following screenshot shows this: