Zend certified PHP/Magento developer

How to tunnel all traffic of a QEMU VM through a Proxy?

I’m trying to make a VM in which all its traffic goes through a proxy (like a tor proxy or any other ip/port proxy). I’ve found this article showing that it is possible in command line, however I’m using the GUI manager (virtual manager) and didn’t found in anywhere a place to setup a proxy for the VM. So I’m asking if is it possible to make through the GUI?

I want to make it on the host machine so it doesn’t happen to make any connection by mistake inside the virtual machine to outside using my default connection.