Your dashboard lives at wa.dunnflow.com/app. It works on a laptop and on a phone browser.
Steps
Enter your business number or the owner's number. A six-digit code arrives on the owner's WhatsApp from your business number within a few seconds. Enter it and you are in for 30 days on that device.
If the code does not arrive
The code is a normal WhatsApp message, so it can only be sent if the owner's number has messaged the business number in the last 24 hours. Send 'hi' from the owner's phone to your business number, then press 'Send again'. Five wrong codes burn the code; request a new one.
Signing out
Settings shows every signed-in device. Sign out one, or all of them at once if a phone is lost.