Both airports, Munich and Innsbruck, are in close proximity to the resort, and the drive from either airport will take about an hour to an hour and a half by car. If you're using public transportation, it will take slightly longer due to transfers and waiting for the necessary routes.
From Munich, you can easily reach the resort by train. You just need to first get to the central train station. You can do this by using the local trains S1 or S8, which will take you to the central station in about 40 minutes. From there, you can purchase tickets for one of the trains heading to Garmisch-Partenkirchen. Depending on the type of train, you will arrive at your destination in approximately 1 hour and 10 minutes to 1 hour and 40 minutes. Trains operate approximately once per hour, and you can find a detailed schedule here.
Another option for traveling from Munich is to take a bus. There are numerous bus services that operate to the resort, and you can find detailed information on this website.
For those arriving in Innsbruck, the website will be helpful as it provides detailed schedules for various routes, including the one to Garmisch-Partenkirchen. The journey from Innsbruck takes about 1 hour and 20 minutes.
