Hey y'all so good news about this achievement is that its unmissable!
You are going to begin in Arthur's office, dont take your pill, continue with your work until you are able to explore! Go and explore the office area, it will lead you eventually to a party! Yayy!!
But eventually you will end up in a chase, dont forget to look up in a particular closet ;) and than continue your journey. After a specific cut scene, you will wake up and the achievement should pop!
P. S. If you want me to change anythin just comment and I will update the guide! :D