Actions requiring sub partner authentication will need your Partner Id, your Partner Token, and your sub partner's Partner Id for the sub partner you wish to access. These values must be concatenated together seperated by a ":" in the format "PartnerId:PartnerToken:SubPartnerId" and then must be BASE64 encoded. The sub partner's Partner Id is not required in all cases such as Account creation. If the The sub partner's Partner Id is not specified the account will be created under the parent partner's account. Alternatively you may authenticate as the sub partner themselves. For either of these scenarios please follow the instructions for Partner Authentication substituting the the sub partner credentials for your own.
Given the partner token "pppppppppppppppppppppppppppppp" and the partner id "00000000-0000-0000-0000-000000000000" and the sub partner id "11111111-1111-1111-1111-111111111111" the concatentated string would be "00000000-0000-0000-0000-000000000000:pppppppppppppppppppppppppppppp:11111111-1111-1111-1111-111111111111". Then that string must be encoded into BASE64, in this case resulting in "MDAwMDAwMDAtMDAwMC0wMDAwLTAwMDAtMDAwMDAwMDAwMDAwOnBwcHBwcHBwcHBwcHBwcHBwcHBwcHBwcHBwcHBwcDoxMTExMTExMS0xMTExLTExMTEtMTExMS0xMTExMTExMTExMTE=". This BASE64 encoded value must be passed in the request as the value of the PartnerAuth parameter.
Alternatively, if the sub partner was setup with a refernece to your internal id using the remoteId parameter you may use the normal Partner Authentication method with the addition of a RemoteSubPartnerId header parameter. The value for the RemoteSubPartnerId should be the base64 encoded remoteId you passed during partner creation.