You'll have to read through the requirements for Canada's various immigration programs to see if you qualify to apply to immigrate. Generally, you need at least one year of full time work experience to apply - in many cases you also need a job offer in Canada. There are also additional requirements (different requirements for each program). Before you can apply, you will have to take a language test and you may also have to have your education officially assessed. You can find detailed information here:
http://www.cic.gc.ca/english/immigrate/apply.asp
You cannot extend your study permit since you are here as an exchange student only. If you want to study as a Masters student in Canada, the first step will be to be accepted by a Masters program in Canada. You can then apply for a study permit specifically to take your Masters (this application will have to be submitted through either your home country visa office or the visa office responsible for your country of residence).