You are asking a very broad question here. What do you intend to study? Best course of action is to call the university you wish to attend (this will likely need to be done long before you apply) and ask what you need to do. TOEFL is one of the requirements, but not the only one. You will also need proof of undergrad degree and transcripts in order for the Univ to even consider that it is valid.
As a GC you will not be considered a foreign student, and why should you? YOu are a Permanent Resident of the US