in edit view in your zenfolio account, go to preferences, then custom domain. on that page, there is a link that will show the instructions on how to setup things on your domain... I have never used melbourneit.com for domain registration, but they should have some kind of 'control panel' or 'settings' page where you create the cname records, etc. per the instructions.
If you have trouble with that, come back here and see if anyone has used melbourneit.com and can walk you through it, or contact support@zenfolio.com and see if they can help.
good luck!
~Kevin
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