You should initially have an account on the Facebook platform at the beginning
1. Then you can access the following link
2.Then click on create account ... as shown in the following picture
3.Then enter your business name , as shown in the following picture
Then it will require you to enter your email business
Note: Do not enter your personal email account because you must separate your personal and professional accounts.
You will be redirected to your newly established business manager. Then you will need to add your assets such as pages, ad accounts and people to work on them
Next picture as an example ...