Facebook Business Pages: How can I add an administrator?

The Problem

You want to add somebody (or your personal account) as administrator for your page, but you get an error.

The Solution

You can easily add administrators by using the e-mail-address (that is known to Facebook), but there are two privacy settings that come into play for that (on the account of the desired administrator):

Step 1: Make sure your likes are public

Step 2: Make sure your profile can be found by using the e-mail address:

--Neno