Most of it will take place at the Johnson Space Center in Houston, Texas, where NASA has a mockup of the Orion crew module, and also at the Kennedy Space Center in Florida, the mission’s launch location.

Source: https://www.digitaltrends.com/space/nasas-moon-astronauts-are-ready-to-start-training/

The Artemis II crew, From left to right: Mission Specialist Jeremy Hansen (CSA), Pilot Victor Glover, Commander Reid Wiseman and Mission Specialist Christina Hammock Koch pose inside an Orion simulator at NASA’s Johnson Space Center in Houston.

Source: https://thepostnewspaper.net/2023/04/08/nasa-selects-crew-for-upcoming-flight-to-moon/

The craft is being built at NASA’s Johnson Space Center in Houston, but it’s being tested at NASA Glenn at its Simulated Lunar Operations Lab.

Source: https://www.limaohio.com/news/2023/02/18/from-ohio-to-the-moon-and-even-mars-nasa-glenn-adds-thrust-to-space-exploration/

This photo shows people attending a NASA Day of Remembrance ceremony on Thursday, January 26, 2023, in the Astronaut Tree Grove at Johnson Space Center in Houston.

Source: https://gizmodo.com/columbia-space-shuttle-nasa-20-years-anniversary-1850048700