Make sure the legal name of your business is mentioned in the header and footer of your website. It is a pre-requisite for Facebook to verify that your website and business manager account are connected.
e.g
An Eikyoo Private Ltd Company.
In the above example 'Twerlo' is a brand name registered under the name of 'Eikyoo Private Ltd'.
Since the documents submitted to Facebook will be under the name of 'Eikyoo Private Ltd' this step is necessary.
Note : If the brand name and company legal name of your business is the same you can ignore this step.