It's very easy by using the subway system S-Bahn or U-Bahns from the Ostbahnhof subway and train station -within sight of the hotel. A 3 to 5 minute walk. In fact the U5 towards Laimer Platz will take you to the Theresienweise stop which is inside the Octoberfest. Last year they did route you through extensive security before you entered the Fest. Much welcomed so leave back packs and bags at the hotel. The front desk can advise you on the right stops and Bahns as well the SBahn staff at the train station.
In fact if arriving at the airport use the S8 to the Ostbahnhof fastest cheapest way. Buy a 3 or 4 day entire network Group ticket at the S Bahn entrance at the airport. Good for up to 5 adults traveling together. Saves you money overall, less hassle and less chance of getting fined for stamping your individual tickets wrong.
Get an answer from Courtyard Munich City East staff and past guests.