Cant connect via comcast please help!

So I just bought a new iMac today and unfortunately I can't connect to the internet via my comcast cable modem using ethernet cables. For whatever reason the mac is not pulling up an ip adress, I went through all the shinanigans with comcast over the phone trying to connect through PPPoE and messing with a bunch of ethernet settings but nothing worked. They scheduled a tech guy to come over Saturday but I really don't want to wait that long.

I'm not tech savvy but if any one could please help me out I'd appreciate it.

I work for comcast, the connect using ppoe should not be checked and the tcp/ip should be set to DHCP not DHCP manually, I"m guessing you have this fixed now, if not let me know I will help. I am an Internet support specialist.