I have found this link to be very helpful;
http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1830/products_feature_guide09186a008008743b.html#22712
Basically you go into config mode and enter a ip dhcp pool <> and that will put you in the DHCP config. If you are using a class C network I would recommend doing one of two things;
1) Set the pool to be address 1-128 and leave 126-254 as static address for your router and servers.
2) Set the pool to be address 1-253 and configure the dhcp server to reserve the address for your servers by MAC address. Then assigned .254 as the router LAN address. This is a bit more administrative overhead but works nicely if you want everything under DHCP control.
I hope this answers your questions if you have any others please let me know....