Make sure you properly entered the Client key(Client ID) and Secret(Client Secret) from the nylas dashboard /settings/general
Secondly under /settings/authentication, make sure you have a valid callback URL that points to your-corteza-domain/auth.
After that you need to make a component in the Nylas dashboard in the your-app/components
We suggest starting with Composer, you can get the componentID that you need from either the URL or if you scroll to the bottom of the configuration page of the component.