Hello, I would like to know how to get to Mutianyu from King's Joy Hotel Beijing?

Kasia, you can walk from your hotel to Qianmen Station of Subway Line 2, take subway line 2 and get off at Dongzhimen Station, get out from Exit E and then find Dongzhimen Transportation Hub. There you can take bus no. 916 Express to Huai Rou North Street. Then change bus from Sha Yu to Dong Tai and get off at Mutianyu Roundabout. The bus departs every 30 minutes. If you don't want to wait, then you can catch a taxi or share a van with other travelers.