Are you looking for the method to know how to make someone an admin on facebook page on mobile, you can follow these simple steps:

1. Open the Facebook app and go to your page
2. Tap on the three horizontal lines.
3. Choose "Page Settings" from the drop-down menu.
4. Click on "Page Roles"
5. Add an admin by typing the person's name under "Assign a New Page Role"
6. Select "Admin" from the dropdown menu
7. Click on "Add" and enter your Facebook password to confirm the action

Now, your selected person will be able to manage your page as an admin.