moved thread to ePO community....
Is the machine already listed in ePO? If not, then you'll need to install an agent on it before it can be controlled. In this situation it might be easiest to get the third party to upgrade VSE which will install an agent in standalone mode. You can then install the agent from the ePO server which converts the agent to managed mode, and it will appear in ePO for you to control.
If it's already under ePO's control, then you can simply move it to the relevant group and let the thrid party manually upgrade the AV.