Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
If you cannot/do not wish to continue paying for your existing mail hosting service, then there are 365 suppliers with whom you can transfer your hosting service to, and the domain registration, and in the purchase of 365 from them you are then able to use your domain address (I'm unsure as to whether this option is available for Home version, it certainly is for 365 business)