Upon entering the bank, follow the wall to your right all the way to the desk in the back corner. The holodisk will be in this desk. To access the safe deposit box, open your Pip-Boy, start playing the holodisk, and immediately exit the Pip-Boy 3000, before or after interacting with the voice activated security system. The security system will tell you that you have been granted access the safe deposit box and it will open.
The audio password for my box is "Nevermore."