If you'd prefer to watch a video tutorial, here it is:

Otherwise, read on and follow the steps below.

Steps to follow:

1. Go to the Domains section and click on Add Custom Domain.

2. Choose your subdomain and ensure you follow the format in the example below.

3. Go to your domain registrar settings e.g. NameCheap and copy the details provided into your DNS settings.

4. Propagation can take up 24 hours. Click on the link provided to check if propagation has started anywhere around the world.

Once one area propagates the rest will follow suit.