If you are in a situation where you have staff that need to work on various Facebook Pages but you do NOT want the client to have the exact names / accounts of the people working on it, using Facebook Business Manager is the best solution.
Here is how to set-up your account, as well as directions you can send to a client, to fully set up your account.
Start by going to: business.facebook.com.
Click Create Account.
Enter a name for your business, select the primary Page and enter your name and work email address.
Move through the rest of the onboarding flow by entering the rest of the required fields.
Once your Business Manager account is set-up, follow these steps for adding your clients and staff members:
REMEMBER: When adding pages, select “Request Access to Page”, DO NOT select “Add Page”
Here are videos you can pass along to clients for them to gather the info needed:
Directions for finding the Facebook Page ID - https://youtu.be/48Ci0-n056Y
Directions for finding the Facebook Ad Account ID - https://youtu.be/8XkMyOqN9Ik