If you don’t have much luggage, it’s most convenient to take the subway.
From Beijing South Railway Station, take Metro Line 14 (direction to Shangezhuang) and get off at Puhuangyu Station, then change to Line 5 (direction to Tiantongyuan North) and get off at Yonghegong Station.
Take Line 14 for 3 stops, then transfer to Line 5 for 9 stops.
Change from Metro Line 4 to Line 2. Just exit Yonghegong Station to the North Gate.

If you don’t have much luggage, it’s most convenient to take the subway.
From Beijing South Railway Station, take Metro Line 14 (direction to Shangezhuang) and get off at Puhuangyu Station, then change to Line 5 (direction to Tiantongyuan North) and get off at Yonghegong Station.
Take Line 14 for 3 stops, then transfer to Line 5 for 9 stops.
Change from Metro Line 4 to Line 2, and exit Yonghegong Station to the North Gate.