Hello jfeltrin and welcome,
If you have a Comcast DPC3939B Gateway, then your private wifi default SSID and encryption passcodes are on the bottom sticker. Your public wifi xfinitywifi SSID uses either your a.) comcast business email address and password, b.) comcast residential email address and password, or the non-comcast user which uses any email address and provides 2 60 minutes accesses over a 30 day timeframe. Lastly, If you have your own business wifi router, you will need to contact whomever configured the setup for you.
Hope this helps you out.