To start with you will need to navigate to the vCloud login page appropriate for the state your "Virtual Data Centers" (vDC) are located, below are links to the different login pages:
Sydney based vDC/s - https://vdc.syd.mhn.net.au/tenant/<organisation_name>
Melbourne based vDC/s - https://vdc.mel.mhn.net.au/tenant/<organisation_name>
Once you are logged into vCloud you can check the amount of resources you have and what is in use by clicking on the icon with the 3 horizontal lines at the top of the screen, then click "Datacenters" from the dropdown.
On the page that opens it will show you all of your vDCs and the resources associated to them, the dials will show you how much of those resources you have in use at the moment
The first thing you would need to do is ensure the resources are not currently in use, you can do this by checking the resources as per the above.
If they are in use you will need to un-allocate them from VMs by powering them off and editing them, or by removing the storage from the VMs.
If you need assistance with removing these resources please don't hesitate to contact our support team who can assist you with this.
When you are ready to decrease the amount of resources you have simply login to the Hosted Network Partner Portal (Link below)
Once logged in click on "SERVICES", then from the drop-down click on "My Services"
Once the page loads click on the vDC from the list that you want to remove the resources from
On the next page, click on "Upgrade/Downgrade Options"
Adjust the values to suite how much you wanted to decrease the resources by adjusting the values in under the title "New Configuration". Once you are happy with the changes select "Click to Continue >>" at the bottom