How to assign organization for user role in dynamics 365?

In dynamics 365, you can grant or revoke user role from an organization 

many times, customer need the user to access organization A only or A& B,...etc

Go to system administration/users /users

and select user

to edit a user, just click on user id

select the role that you need to assign organization and click assign organizations 

you can access grant access all organization by click Grant access to all organizations

or grant access to specific organization individually  by choosing one of the organization hierarchy  

or Grant with children on organization hierarchy  

you can revoke access by click revoke 

Thanks.