Well it depends on the program, but for the most part:
you must have been accepted to a Canadian educational institution
you must be able to prove you have enough money
you must be admissible: i.e. you must not have a criminal record or a medical condition that renders you inadmissible
you must demonstrate that you intend to return to Brazil after you finish your studies
Please note that the rules are changing in June. See this article: https://www.immigroup.com/news/new-rules-international-students-studying-canada-june-1-2014