Hi Lugboso, in order for you to apply, you should first check if you have fulfilled the following:
ou need the following documents to apply for a study permit:
Proof of acceptance in the form of letter of admission
Proof of identity in the form of a passport and may be passport-sized pics
Proof of financial support by letter from sponsor, bank loan, scholarship etc
Letter of explanation which is optional and meant to highlight your study plan while in Candada
For your second question, it is best when a person is directly related to you by blood i.e. father, sister, brother or sister is the sponsor. But it doesn't stop your uncle,aunt, cousin or guardian from being your sponsor. Another option to consider is presenting a student loan from a bank. Since i'm not allowed to post links you should google cic's website for more info.
I hope my answers will help you somehow!