If you were granted asylum status in South Africa, then there is really no way to apply for asylum in Canada.
If you wish to immigrate to Canada, you will need to apply through one of the economic immigration streams like Express Entry based on your work experience, education, etc.
Only way to get to Canada is to apply for PR. Curious why you want to claim Asylum in Canada after gaining it in South Africa. People genuinely claiming asylum do it because their life is in danger and only care that they are not in danger.