When you’ve successfully landed on the page that you want, scroll down to the Settings feature on the left sidebar. Within the Page Settings, navigate to Page Roles. This can be found on the left sidebar as well.
Under Page Roles, find the option to “Assign A New Page Role”. Here, you can enter the name of the Facebook user of who you want to add as a new manager. Specify that you want to add them as an Admin using the drop-down feature to the right. When ready, simply select “Add”.
Once you’ve added them, that person will be able to go to their business manager account, and they’ll be able to request access to the page. Notify them that you’ve added them as an admin and be sure that they follow through to successfully become a page manager.