Obviously, you need to pick locks. There're plenty of videos on YT how to do this. HOWEVER, you can boost this a little when on the Empty Nest mission with Sam Coe in the Bank in Akila City. When you are tasked with "Search for the Maps" make sure you pick every Secure Storage Locker in the Bank Vault. There's around 10 of them.
You can also hack bank ATMs, but you'll probably get nabbed by the authorities!
You can always save before attempting to pick a lock in case you fail.