It's been quite a few years since I have touched one of those, but the basics you need to do are:
1 - in the signalling section of the navigation tree in the software, you need to create a MDC signalling system if one does not already exist.
2 - assign yourself a radio ID, even if you are not going to transmit the MDC.
3 - in your channel personality, there should be a signalling drop down to select that MDC system you created.
In all of my VHF radios, I have them setup to decode MDC on all of the channels, but I do not transmit. So, if anyone is using it, I will see their ID on my screen.
In the general radio setup, there is 1 more place where you may need to check, emergency revert. I don't remember if you need to do anything with it, but it might be some place that could throw an error at you.