Both,
Unfortunately the “try it out” function on the developer site for document metadata and document retrievals is broken, and needs to be resolved. Once fixed you will not be required to enter the authorization field as this is provided by the API key selected.
Apologies for the error on this page and will look to resolve as soon as possible.
With regards to retrieving documents and authorisation the attached post maybe of interest.
Apologies for the frustration.
Thanks,