Add Custom Domains

In order to add/use a custom domain with your links, ensure to point it first to your web hosting, to the same server/hosting/IP by adding an "A" DNS Record (from your Cpanel or domain provider) in order to function properly. For adding your whole domain as Custom Domain:

TYPE            HOST            VALUE
 A               @                your-hosting-IP
 A              www               your-hosting-IP

For adding your subdomain as a Custom Domain (https://sub.domain.com):

TYPE            HOST            VALUE
 A              sub              your-hosting-IP

DNS records may take up to 24 hours to take effect (but usually, it takes just about 15 to 30 minutes).

Then, add an "alias" to your main domain from your Hosting provider (e.g. Cpanel, Plesk, DirectAdmin) (see tutorial video): https://www.youtube.com/watch?v=pwKUvIVT3No