There are two types of powers of attorney: (i) immediate powers of attorney, and (ii) springing powers of attorney. Immediate powers of attorney are effective immediately, with the agent being able to use the POA immediately after the person signs the document. A springing power of attorney doesn't convey the right to step into the principal's shoes until the person becomes incapacitated. Normally there's a clause in the document requiring a doctor's note or letter to be attached for you to use the DPOA. It's important to know which kind you have so that you know if you need a doctor's certificate to attach to the DPOA before you use it.

Second, there is no registry or filing place for DPOAs. You just keep the document and use it on a case by case basis where ever you want to act on behalf of the principal. So if you want to write checks for mom, who named you as her attorney-in-fact in her DPOA, you take the document to the bank, and they will clear checks that you sign on mom's account.