You manage all your domain settings yourself, including domain registration and DNS.
For this you will need to configure your domain to point at the appropriate server. You will need to update these settings on request where necessary. For instance, when moving your website to another server.
You will pay your domain provider as normal. I require an admin fee for externally managed domain. This is to cover the extra effort created when I don’t have access to the domain name and DNS settings (e.g. when managing the web server).