How can I get to the Great Wall at Huangyaguan from Nikko hotel 189 Ningjing rd Heping District

Trev, you may take a taxi from your hotel to Jianchangdao Passenger Transport Center (also called Hebei Passenger Transport Center). There you can catch bus to Jixian. If you catch a taxi from Jixian to Huangyaguan, it should cost around CNY 50. Otherwise, you may share a van with other passengers. It costs around CNY 10.