Movie theater. They were showing a movie about demons, and the demons came out of the screen. Lots of people die in cool ways. There, now you can remember the plot.
I'm pretty sure the movie that the girl is watching in part 2 is about the events of the first film. It's been awhile.
The sequel is about how a giant portion of the city is walled off after the first demon attack or something and she's watching a documentary about them exploring the ruins or something and then a demon comes through the TV.