How to use Codeforces API to compose a request to use a person api key to authenticate that request.

I keep on getting the error : "You have to be authenticated to use this method".

Eg: "{u'status': u'FAILED', u'comment': u'apiKey: Incorrect signature;onlyOnline: You have to be authenticated to use this method'}"

if there anyone can help or give me an exapmle of request ?