Actions requiring account authentication will need the Account Token and your User Token for the account you wish to access. These values must be concatenated together seperated by a ":" in the format "AccountToken:UserToken" and then must be BASE64 encoded.

Given the account token "aaaaaaaaAaaaaaaa" and the user token "uuuuuuuuuuUuuuuuuuuu" the concatentated string would be "aaaaaaaaAaaaaaaa:uuuuuuuuuuUuuuuuuuuu". Then that string must be encoded into BASE64, in this case resulting in "YWFhYWFhYWFBYWFhYWFhYTp1dXV1dXV1dXV1VXV1dXV1dXV1dQ==". This BASE64 encoded value must be passed in the request as the value of the AccountAuth parameter.