You'll need a Lionel TPC unit or a Legacy Powermaster.
( one of the newer zw's might have one already integrated into the transformer? Not sure)
Either component will allow Legacy handheld control of speed, direction, whistle,bell,electrocouplers, and some of the passenger/freight announcements.
I operated a few MTH PS 2 locos via a TPC unit. Once under way. It was hard to tell they weren't under cc. They ran very well. Also smoked like crazy, which is adjustable manually via the smoke "pot" on the tender
Additionally , since MTH locos already have a battery or bcr as part of the electronics. Lights and sound do not drop out during conventional direction changes.