By "chapter 1," do you mean the "Red Harvest" ending?
If so, after you complete Red Harvest, start the game again from the beginning. This time, there will be more choices after the first one (in which you can choose if Shogo tries to kill Isabel or not -- yes leads to the bad end, no to Red Harvest). This time, later on, there will be more choices about how Shogo interacts with other characters, especially (but not only) Carol. If you consistently choose the options that imply more empathy to the Disaster Witches and their plight (rather than Shogo's usually detached attitude), then by the end of the interlude you should get a screen saying "Ashes and Diamonds"... and from then on it's the other ending (personally, the one I prefer).
Now, if by "chapter 1" you simply mean the first part after the prologue, i.e. "Tales of Ordinary Madness"... then you should simply go on playing. As far as I recall, the action doesn't stop after "Tales of Ordinary Madness," you just continue through, and chapter 2 starts automatically.