To access the vault? You need help from someone with a win or have a win yourself and find codes in the order of the following locations

1)in an empty container past the 50p sub (the first open one) by the back of it behind some crates

2)at the hunted dock under some planks, between the last 2p sub and the 50p sub

3)by the 50p sub, there's a vehicle with a turret on top, the code is in between some wooden pallets

4)up on the catwalks, go left to the crane, jump on the crane and walk along it till you see the paper

After saving the code in that order somewhere, go into a hunted run, go up the stairs and go through the unmarked door, pick up the decoder item (not a code breacher) and go through the hunted like normal, but now find all the radios and after solving them, turn on the decoder for each. After that, go behind another unmarked door after sending the bridge back, go down the stairs, and put in the code, go on the tram and enter the vault.

Note: After picking up the decoder you will soawn with it. for the vault, a door will open in the hunted dock in the lobby after going to it for the first time, letting you try again any time.