To buy your domain, you can head across to www.domains.co.za. As discussed in this lesson, you can buy the domain with hosting if you would like to have a website and email with the domain.
It is advisable for you to purchase an SSL with the domain as it will solidify your domain as safe. The main difference is that your domain will be presented as https:// as opposed to http:// and what this means is that when someone visits your site, google will not flag your site as unsafe. If you already have a domain, contact your hosting to set up an SSL on your website.
There are obviously plenty of other hosting providers, so please don’t feel you need to use domains.co.za
Any questions please do let me know!