How to use sub-domains in multisite

Hi guys

I recently introduced two sub-domains to my sites list in my WP Multi-site. They don't yet work and I was wondering what step I don't understand correctly.

Basically I want to introduce the following new sud domains to my site:
1. webdesign.succeedonline.co.za
2. ptyltdcompanyregistration.succeedonline.co.za

I created these in the sites dashboard and waited with the hope that they start working automagically. Unfortunately they did not start working. I then headed to CPanel and created these subdomains there but they are searching for sub-folders and therefore don't work either.

I see there is some instructions on editing DNS records on your instructions. I do however not yet understand the background. Should I create a sub-domain and edit the DNS records or not?

Thanks
Johann