You have to be a Landstar carrier.
Landstar works with O/O only and you will need your own authority. Contact the agents directly and get set up in their system they will require a contract between them and you. I usually call and let them know my availability and if they have something come in that matches what I'm driving they call me. Ive run several loads for them and never had a problem getting paid or factoring the invoice. As long as you have a clear BOL, Invoice and rate sheet your good to go.