Provider setup
Some connections your customers make involve a third party asking them for permission. By default that permission screen would carry our name. Registering your own applications with those providers puts your name there instead, so the white label holds all the way through.
This is set up once, in the partner portal, and it covers three providers: Google, Cal.com, and Calendly.
Why it matters
Two things change once a provider is configured for your program.
Your customers see your name. When someone connects their calendar, the provider's consent screen names the application asking for access. Without your own registration, that is not you.
Google sign-in appears on your domain. On a partner domain, the Sign in with Google button is only shown when you have configured Google yourself. Until then your customers sign in with an email address and password only — the button is hidden rather than broken, so it is easy to miss that it is missing.
Setting one up
You register an application with the provider, in your own account there, and then enter what it gives you into the portal's Integrations screen. The portal shows each provider as configured or not configured, so you can see at a glance what is still outstanding.
The provider will ask where to send people back to after they approve access. The portal shows you the exact value to use — copy it from there rather than typing it, since a mismatch is the usual reason a connection fails at the last step.
Treat the values the provider gives you like passwords. If one may have been exposed, replace it at the provider and update it in the portal.
What your customers do afterwards
Nothing changes for them. They connect their calendar the ordinary way, from their own workspace — see Integrations. The only difference is whose name they see while doing it.
If you skip it
Your program still works. Customers can still use the product, and connections that do not involve a consent screen are unaffected. What you lose is the consistency: the one moment where a customer is handed to a third party is the moment the branding would otherwise slip.