train from Milan.

Just enter "Milano Centrale" as departure station and your final destination in Sicily as the arrival one on www.trenitalia.com/en.html ? Then click search and let the site do its job.

That's the longest train ride in Italy, trains slow down south of Salerno.

Milan to Palermo by train is something like 16 hours or more, at this time usually with a change somewhere (Rome or Naples), a ferry crossing and most solutions involve traveling by night. Flying is much easier and faster.

I don't know what you mean by jump off city, but if you want to go to Sicily, you buy a ticket to Sicily. Or rather a town on Sicily. It's an easy train trip using the night train https://www.seat61.com/international-trains/trains-from-Milan.htm#Milan-Sicily

I had an absolutely miserable, 100%-sleepless night in a couchetter berth on that night train back in 2015. The rails south of Rome seemed in very poor condition, so the rail carriage jerked constantly from side to side. Not having slept at all, I crashed as soon as I'm got into my hotel room in Catania, which meant that my body clock,was messed up for more than 24 hours. I heartily recommend flying or stopping overnight in one or two interesting 0laces along the way.

Thanks for all the info. after reading I have decided to alter my plans.