You don’t. You just connect your primecare devices to the Fusionhub and they will connect - even if your Fusionhub does not have enough peer licenses, because a primecare device does not consume a hub peer license.
If you want to migrate from a lower license level fusionhub to a bigger license count you’ll need to backup the config of the current hub, destroy it, build the new one apply the license then restore the config.