I don't know that particular song, Mbo, but here are some general thoughts. Explain that the song is so good you have to sing it, regardless of its point of view. If appropriate, you could throw out a humorous line, like "I used to sing this before my sex-change operation" or "just imagine me in hose and heels, with a curvier figure". You may find no introduction/explanation is needed at all. Generally the audience will catch on that the song's narrator is female and that you are male, and make the necessary psychological adjustment.