Connect two lan segments in AD with ADSL modems

Hello.

Please help me with this issue:
I have to connect two lan segments through ADSL. The first is already in AD and i want to add the seccond one in domain.

Let’s take this example:
1.) 10.10.10.X – the first lan wich is in domain with 2003 server.
2.) 10.10.20.X – the seccond lan wich i have to add it to domain.

I have two adsl modems Thomson 605s.
Where i should do the settings? In AD server or in modems? And how to config them?

Thank you very much. Vasi.