If you are an existing Nexmo user with an account that is no longer in trial status (has been taken out of Demo mode), you can begin to use the Number Insight APIs without any additional configuration changes (permissions). All you need for a request is to have your API credentials: (account) key and secret, and some balance in your account. In addition, you will need to have an HTTP server to host a callback reader to consume the information returned for your Number Insight query.
Please note that in order to be compliant with the various data protection laws around the globe, you must have consent from owners of the phone numbers to use Number Insight depending on the country that the phone owner is in. If you are unsure what this means for your application, please get in touch with your account manager or contact firstname.lastname@example.org