You move your cursor over to PI's name and click it. After a few seconds which feels like several hours, he responds and you start chatting.
You and he proceed to have the very first conversation in this story (if you neglect the sans conversation) starting with PI saying "WH4T'5 UP M4N" and ending with him starting to download Sburb, and saying, "see ya!"
You then start playing Sburb, getting out a bar of gum along the way, snorting it out, cleaning it up, shooting a trapdoor and playing the duckhunt game, finding out that you did in fact eat those seeds and didn't captchalogue them, and finally getting your pal Meowrage into the Medium. Before of course, talking to MM and SK about the game along the way, until you finally reach the last moment in act 1.
SB: Meowrage? Your house, it looks different.