To add facebook neighbors, go settings and login to facebook.
Once logged in, hit the blue button at the top of the screen (with the face and + sign). It will show your facebook friends. Check the ones you wish to add.
An invite will go to them. Once they accept the invite, you should be neighbors.
To find more facebook friends, you can post on the facebook app page.
https://www.facebook.com/DiamondQuestApp/?fref=ts