If they have a will, their appointed executor locates the will, applies to the courts for a ‘Grant of Probate’, approaches financial institutions to close accounts, distributes assets from the accounts according to the will.
If they don’t have a will, someone step up to represent the deceased in the middle of your family’s grief. Others who qualify must give their written consent.
They must create a Schedule of Assets, and apply to the court for ‘Letter of Administration’, and once granted, approach financial institutions, and then distribute assets according to the state’s own formula. You and your family have no say.