You can create your own API Key and access Resmo via Rest API. Creating an API key is an easy step that you can manage from Settings -> Integration -> Rest API Management tab.
You can manage scopes and expiration details of an API key on this tab. You will also have to enable disable option for your API key.
In Resmo API, all requests must be authenticated with a bearer token.
Use the HTTP header Authorization with the value Bearer, where the token is the API key that you created in Resmo.