|If you have a SOHO router in place, you shouldn't need them, just plug the xbox into the router.|
If you don't have one, you should. But between now and when you have one, the PPPOe settings (ie: username/password) should have come from your ISP with your highspeed connection.
You know what, for the time it takes, I highly recommend googling something like "connecting xbox 360 to the internet". You're likely to find a whole lot of info out there. If it were me, I'd start looking on the xbox 360 website. There's likely to be some networking info available there too.