Is it DSL or Cable modem ? Are you having a static IP or a dynamically assigned IP ? The 837 has an ethernet port you connect that to the modem's ethernet interface. Mostly all modems support DHCP so your router's ethernet interface should get a lease IP address. Add a default route on the 837 router pointing to the modem. PCs behind the router should be configured with a default gateway as the router.
PC ----ethernet---e0routere1----ethernet---DSLmodem--Internet.
Hope that helps!
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus