|The following is based on Fallout: Brotherhood of Steel and has not been confirmed by canon sources.|
After the Initiate has made their way through the Facilities and finally back in the garden, they can speak with Patty to get information on the new situation. She'll give the Initiate the ruins keycard so they may enter the ruins.
A keycard, existing of many colors. It opens the door the Ruins One, west of the Gardens area.