I am co-executor of the will of my late husband and it may become necessary to open a bank account for the estate. What do I need to do? Thanks

Normally a notice or letter from the probate judge showing who the executor of the estate is, and normally a EIN number from the IRS.
You can call and get a number over the phone.

But you may tak to your bank, a small home town bank that knows everyone by name may require less.