API to create a package in sender account

when I tried to create a package using API call to my sender account (not the owner), even in the header, I put the sender API key there, but I got error message as 

{
    "code" : 401,
    "messageKey" : "error.unauthorised.noSession",
    "message" : "Failed to retrieve Session",
    "name" : "Unauthorized"
}

what's the proper way to create a package to sender account using API?

thanks,

Cindy