I have just registered, do I already have a vendor number or I should first get appointed?
If you are talking about your registration here on MarketSqr, then you will not get assigned a vendor number. We are an independent supply community.
You are probably looking to register on the Central Supplier Database of the South African government. Once you have completed the registration there, you will obtain a supplier number (typically starting with "MAAA..."
For support in the registration process, look for the "Help" and "Contact" options on the top menu of the CSD.