How to use domain windows user account as app pool identity

I will be using a domain windows account(maintained in Active Directory) as Application pool identity in my web server. So i want the account to be a member of IIS_WPG or IIS_IUSRS group. My question is where to do it? in Active Directory or in the web server itself? If i modify the Active Directory, so that the user is part of IIS_WPG/IIS_IUSRS, should be more than enough? or i should edit local users/group(in web server) to make sure i add the domain user to IIS_WPG or IIS_IUSRS group?