How do I go from temporary residence permit to temporary working residence permit?

I am currently on a temporary residence permit (just for living). I have work lined up with a company that can provide working visas. I want to apply for a temporary working residence permit next year. How do I go about it?? Do I have to go to Hong Kong and re-enter china with the working visa ten apply for a temporary working residence permit? or can I stay in china and change it? Also when can I do it? Can I do it 3 months before my current temporary residence permit expires?
Thank you for your help =)