SETTLE|MY|YOUR DOCTOR CLIENT ID: WHERE'S MINE?

So, we just need to pay my doctor's bill. Easy, right? Not so fast! The website says I need enter my Client ID, but where is mine? This whole situation is making me crazy! I've looked everywhere, but this darn Client ID seems to be missing. Maybe I just missed it? Could someone reach out to customer assistance? Help! This is becoming a hea