Open business setting page https://business.facebook.com/

And select business account where you want to change user/people role.

Scroll down to the end.

On same left side menu bar, select Setting option from Setting and help menu.

Click on People settings option and click on user name that you want to update.

When you click on name, it’ll show you more settings where you can update user/people role of your business page. Click on Manage button.

A popup box will appear to be. From Business account role option you can changerole of people linked within your business account.  

Then click on save button.