The ADSL wic is nothing but a modem. It has a built in phone port to which the phone line can be directly connected. Typically, the CPE (DSL modem) is provided by the service provider and then you can run an RJ45 cable from DSL modem to the router. But Cisco's wic can be used in situations where you want to just manage one box, compared to managing 2 boxes. Also if the router has a direct connection to the DSL line, tracking the DSL interface status is easy, compared to using an external DSL modem via ethernet interface.
You can find various sample configs here.
http://www.cisco.com/en/US/tech/tk175/tk819/tech_configuration_examples_list.html
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus