Add them to your config file along with your domains. Leave consumer_key empty for now (see config.yaml.example).
Run the setup to request a consumer key scoped to your configured domains:
./waybackd -setup
This prints a consumer_key and a validation URL to stdout. Open the URL in your browser, log in to your OVH account, and approve the request (select "Unlimited" validity to avoid expiration). Once validated, copy the consumer_key into your config file.
The following access rules are requested per domain: