Bozen-Bolzano is located in the center of the Alps, next to the main connection between Italy and Central/Northern Europe at the Brenner pass. There are plenty of apps ad websites out there for comparing, combining and booking trains and buses and flights.
The most used airports for travel to Bozen-Bolzano are Milan and Munich, but there are also closer airports in Innsbruck, Verona, and Bologna that may be useful.
From Milan, Verona and Bologna, regional trains (e.g, by Trenitalia or Italo) are the cheapest options, but there exist also direct bus services.
From Munich, direct international trains (e.g., DB Bahn and OBB) leave to Bozen-Bolzano every two hours, while a cheaper option are buses operated by Flixbus.
Coming by car, use the Brennero A22 motorway and take the exit Bolzano-Sud if you come from the South (Verona – Trento), and Bolzano-Nord if you come from the North (Munich – Innsbruck).