Visas are required for entry into South Africa for certain passport holders.
To see if you require a visa please visit http://www.home-affairs.gov.za/index.php/types-of-visas
For information on passport holders who are exempt from visas for South Africa please visit http://www.home-affairs.gov.za/index.php/countries-exempt-from-sa-visas.
For information on applying for a South African visa please visit http://www.dha.gov.za/index.php/applying-for-sa-visa
An invitation letter to help you with your visa application is available online here