Attaching the collar clarification

Hi! This is my first time sewing this shirt, and I'm struggling a little with the instructions for attaching the collar. The pattern says "pin the under collar to the shirt's neckline, right sides together." I assumed this meant to the outside of the shirt rather than the inside, but then it occurred to me that because the yoke has right sides out both on the inside and out, maybe I'm wrong? The diagram looks like the under collar is being sewn to the inside of the shirt. However, the next diagram shown with the instructions for blindstitching the upper collar also look like this is occurring on the inside of the shirt. Does anyone know which way this ought to be sewn? Thanks!!