Actions requiring partner authentication will need the Partner Token and your Partner Id for the account you wish to access. These values must be concatenated together seperated by a ":" in the format "PartnerId:PartnerToken" and then must be BASE64 encoded.
Given the partner token "pppppppppppppppppppppppppppppp" and the partner id "00000000-0000-0000-0000-000000000000" the concatentated string would be "00000000-0000-0000-0000-000000000000:pppppppppppppppppppppppppppppp". Then that string must be encoded into BASE64, in this case resulting in "MDAwMDAwMDAtMDAwMC0wMDAwLTAwMDAtMDAwMDAwMDAwMDAwOnBwcHBwcHBwcHBwcHBwcHBwcHBwcHBwcHBwcHBwcA==". This BASE64 encoded value must be passed in the request as the value of the PartnerAuth parameter.