How do I set MPUtils up to do the new version notification?

There's nothing on the wiki.

And there's nothing in the relevant config file.

...

so how than?

Its done via your mpinfo file. Anytime you change the version in that, it will notify the user to look at the change log. Its only client side though, so if your wanting to use it to inform a player of a new update to download. It doesn't do that. Only meant to try and get the player to look at the current change log if the version changed. TBH its not a widely used feature, hence why it was never properly documented. Its either going to be changed or removed at some point.