To add an admin to a Facebook page, first, go to the Pages option in the left-hand column on Facebook.com. If you don't see it, click on See more and scroll through the options.

Add Facebook page admins on the mobile app or website Tap the menu or profile icon in the upper-right corner. Tap the drop-down arrow beside your account name to switch to your page.

Click on Page Role. Go to Assign a New Page Role, in the field, type the username or email ID of the person you want to give the position of admin, select their profile, and set Admin. Click Add.