i dont understand what does it mean by second act? What should i do? 
That was the step-by-step instruction. There are only two steps :) But you can see the hints on the piece of paper on the wall in the main character's room. It tells you about major events. You should have had a tutorial on this paper before. Most likely, you had a major event starting, but you clicked “delay” it, and therefore, the button to start it is now in the main character's computer