AFAIK it’s on by default since 4.24, so you should be able to see some “New Engine” asset types like the SourceBus and Submix families, in the Content Browser > Add New > Sounds tab.
Further more, go to the Edit > PlugIns > Audio tab, turn all the lights ON and start the party !
And well… I wouldn’t build my party around TimeSynth, unless I’m stuck on 4.25 forever. Just saying.