Train Milan to Turin

You don't even have to go into Milan to the train station to head to Turin. There are direct buses to Turin from the Milan airport.

Assuming you're flying into Milan Malpensa Airport aka MXP you need to take the train to Milan Centrale (~1 hr) to take a train to Turin. Trains to Turin are about 1 hour for the fast trains and 2 hours for the regular trains and run about 2/hour all day long.

You can check ticket options on state run Trenitalia (using Milano and Torino) to check times and options: https://www.trenitalia.com/en.html
or the privately owned: https://www.italotreno.com/en which also runs fast trains.

Fast train tickets can be purchased in advance at a discount but because you can't know specifically when you'll be ready - flight delays, immigration, etc - it probably just makes the most sense to buy the tickets to Turin when you know you're ready in Milano Centrale.

Both train companies have apps for booking tickets and tracking trains.

Have a great trip,
=Tod

Assuming you're flying into Milan Malpensa Airport aka MXP you need to take the train to Milan Centrale

This isn't true. The passenger just needs to check train schedules from Malpensa to Torino on the desired dates using trainline.com or an app such as TrenIT! (the Trenitalia app). Any changes of train will show up on the website or app. Note that there are several train stations at MXP, and passengers should know which terminal their flight arrives at in order to plan a train ride to Torino.

Malpensa is a fair distance west of Milano. It's unlikely the best train(s) to Torino will transit through Milano Centrale.

Bus info linked in this thread
https://community.ricksteves.com/travel-forum/italy/question-about-customs-in-milan