need help with router to routermodem

I need help setting up my router with tomato installed, relevant to a router/modem given by my isp.
I don't know if this is correct, but this is the configuration I attempted:

1) make router/modem into modem
1a) Disable DHCP on router/modem
1b) Disable wireless radio on router/modem
1c) Disable NAT on router/modem??? should I do this?
1d) Keep PPPoe on router/modem because this is what connects to internet

2) make tomato router handle DHCP
2a) how do I do this?...

need help with router to routermodem