Go into your "Practice Information" in "Administrative Options". For your practice address, on the first line put "EIN #xx-xxxxxxx". On the second line, put your street address. Your EIN will print under your name on the superbill. If you choose, you could probably fit your NPI on the same line.
As to security...I agree that we should protect our social security numbers. I believe that your tax ID is actually public information, so while you may not want to broadcast it, it isn't exactly a secret, either.
