The guests who are viewing are the audience and spectators. That's all that viewers who are guests at a location do, right? Makes total sense.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
I went to my first American rock concert yesterday and was surprised when the audience suddenly started fighting each other.
That comedian is well-mannered toward the audience, but bad-mannered toward the staff.
I went to a concert with Salmon and surprisingly, everyone else in the audience was a Sumo wrestler.