re: "I have a freelancer but don't know how to submit a proposal."
I am sorry, but we do not understand what you mean.
Do you mean:
a) "I am a freelancer. I do not know how to submit a proposal."
b) "I am a client. I have found a freelancer I would like to work with, but I do not know how to create a job posting that he can apply to so that I can hire him."
c) Something else?