If you had his password you could get in but you are not supposed to and you would be committing fraud I think if you touched his money.
Who are the executors of his will (if he had one)- they should contact the bank
I see from your other post that you are still married. You should not touch his account until you've asked the bank what to do. They will probably ask about probate and executors unless the amounts involved are small.
The bank may just ask you to sign an indemnity. It's far better to do this properly than risk finding yourself being accused of theft. You need to tell the bank (take a copy of the death certificate and any papers if you are an executor) - they need to know and are used to helping in these situations