A quick perusal of the BJ subway map would show there is no 'direct' as in no change route to Tian'an'men. Although I'm not sure that is actually where your hotel is (it's east of the FC and the nearest subway stop seems to be wangfujing).

A cab will cost you about US$20, which is excellent value imo and by far the best way to get to your hotel -- will take half or less than the time of public transport. For public transport options -- try google maps. It is pretty good for Beijing.

tb