Ok, so there's 6 tile entities that act as buttons in front of the bunker a little to the left. If you hover your mouse over them with context menu open you will see them.

here's a diagram:
[1][2][3] ^
[4][5][6] | Door this way

assuming that you have users individually set up to hit each button and you follow my diagram, as of right now the code should be 4 - 2 - 3
after which the door should slide open given that you inputted the code relatively quickly

(NOOO YOU CANT JUST POST THE CODE PEOPLE SHOULD WORK TO FIND IT!!!, haha discussion page go brrrrr)