You would be able to transfer your domain over to Afrihost so they can control your DNS by signing up as a transfer. Or if you want your website to stay exactly as is, but only have AH host the mails, you could sign up a mail package as self managed, and they will tell you where to point your MX records.
If you are hosting your site through something like WIX, then it may be better to transfer the domain, and then Afrihost can point your website to wherever you need it to be.