Hi @seanw.i0nlgo and welcome to the Community!
The article you reference that mentions integrating service is for calling international numbers other than Canadian numbers. Is that what you wish to do (be able to call European numbers while traveling there)? I ask because none of the services mentioned in that specific article provide cellular coverage in Europe and would be limited to when your phone is connected to WiFi there.
In any event, quoting from that article:
Integrating Your International Service
The method for integrating your new international service varies depending on phone model. I’ve arranged for testing on as many models as possible. That said, if the phone specific guidance doesn’t work for you, please try Zoiper.
Unfortunately, some manufacturer’s modify Android sufficiently that integrating doesn’t work, so a separate app (I suggest Zoiper) is necessary. The entire article is linked here: Calling International Numbers with a Republic Phone.
If the goal is cellular coverage in Europe that’s a different process and would involve acquisition of an alternative local (in country) SIM from a service provider other than Republic. More detail on all that is linked here: International Travel with a Republic Phone.