Office 365 -Enabling Targeted Release for the entire Tenant

Hi ,

  I would like to know how to enable Targeted Release for the entire tenant. As far as I know , there's an option to enable targeted release for all the users in the tenant as well as for selected users in the tenant . However, I'd like to know how to enable that for the entire tenant .I see many Microsoft blog articles which states that few new features are only available for the tenants which are in targeted release and hence I'd like to know how to enable that for the entire tenant . Please check and let me know .