Instructions on how to open

1st Outer door:

-Leads into the bunker and is not locked, once you go deep enough in you will come across a 2nd Locked door.

2nd Inner door:

-Open as of Season 5: This video/code was released on Day 4, August 17: On Tape 1977-78 (Pink Dot)
-Code: 97264138

This is part of a massive community effort all started off by activision with clues leading to this website:- https://pawntakespawn.com/tv
A good explination of this was made in a video by JackFrag :- Video

Inside you will find:-
On Day 4, players almost immediately realized that B7 corresponded with Bunker 1 near the bottom left of the map, by the racetrack. Using the code 97264138 allowed players to get inside.

The interior of the bunker is a bit boring compared to the others, however, there are still a few interesting things. For one, the tires and front bumper for the RC-XD found in the Prison Shed on Day 3 were found in this bunker. In addition, there's yet another mysterious elevator which, like the one found on Day 2, is currently inoperable.

I also Took Screenshots of what looks like Puzzles/Clues to a BIGGER puzzle, see below:-