I have a WorkCentre 7775 and I need to be able to print to this machine from home. However, I am unable to work out a way to accomplish this.
Is there something I am missing? Is this not supported by this model?
You need to be able to access the printer via it's host name or IP address, this is the same inside and outside of the network.
The method of doing that is up to the network admin and is unrelated to the printer.
You could, supply a public static IP, or port forward to the device to make it available to the Internet at large, but this is an absolutely terrible idea, but people do so, because those printers get indexed and can be found quickly with a google search.
The much better way is to create a VPN that users can remote into the network from home, once they have access to the network they can print or do anything else as if they were there at the office.
If the printer has a DFE like a Fiery, there are other methods such as EFI Print Me.
Google Cloud Print is likely to be the simplest in terms of setup.