This only registers the dealership here. Nothing is deployed until you press Provision on its Deploy tab — so this is also how you add a site that already exists: register it, fill in its deployment facts, then connect it from the Hub connection tab.
Registered. This ingest key is shown once. If the dealer's site already exists, set both variables on its Railway service and redeploy — it streams its whole history on first sync. If you will provision from the Deploy tab, ignore it: provisioning installs a fresh key.