Quick 6 minute complete guide with timestamps.
https://youtu.be/isx2OtRM2DI
Step 1: Shoot All 5 Freddy Nursery Rhymes On Walls Throughout Map
Step 2: Locate The Room That Is Now Opened (It Is By Speed Cola)
Step 3: Interact & Try To Wake Up (This Starts The Boss Fight) Might Want To Prepare First
Step 4: Kill Freddy Or Just Stay Alive. There Are Three Total Areas (Nightmare Locations) To Survive Or Kill Freddy During Boss Fight
Step 5: You Are Awarded A Perkaholic And The Buy-able Ending Is Now Unlocked
Step 6: Collect 35,000 Points & Purchase Buy-able Ending To Escape Freddy… For Now..