Adding a Facebook Admin to your business page is an easy process.  Here are the steps you need to take to grant someone admin access to your facebook page.

1. Go to https://business.facebook.com/ and log in with the credentials that you use for your personal Facebook page.
2. Select your business page from the dropdown on the left by clicking on the down arrow and selecting your business name.
   
3. Click on the “settings” button on the lower left side of the sidebar.
   
4. Click on the “people” button on the sidebar and the then the “Add People” button on the right.
   
5. Enter the email address of the person that you wish to add to Facebook page.
   
6. Select “admin”
7. Click “next”
8. Under the section called “Select Assets” select your business name again.
   
9. On the right panel, select “Manage Page”
10. Click “Send Invitation”

That’s it!  The person will receive an email asking them to accept the invitation and once they accept, you’ll receive a notification that they have accepted.