I am not sure about walk in ,in india you have to pay a fee for 2 way courier then you will get a awb number and blue dart will pick from your home.
You need passport
Ppr letter
2 pic (according to their spec attested by the photographer)
They will send an email once you pay you have to take a print out and place it inside the envelope
Vfs consent form
If any extra documents is asked then add It
Your height weight eye color sheet
@stirredo did I miss something
I shared a video before, I am not able to find the link now