The ACS documentation is here:
http://www.cisco.com/univercd/cc/td/doc/product/access/acs_soft/csacs4nt/index.htm
but this is limited when it comes to specifics about router configuration, simply because there's potentially 1000's of different types of NAS's out there and it would be impossible to detail all of them. ACS has been specifically designed not just for Cisco devices but for literally anything that runs Radius/TACACS.
For router configuration details, check the router doco here:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fsecur_c/fsaaa/index.htm
Hope that helps. I would recommend you start off very slow and just configure authentication for logins, which is as basic as:
aaa new-model
aaa authentication login default group radius
radius-server host x.x.x.x key cisco123
Then on ACS add the router in under Network Configuration, and add the user in under User Configuration.
Start adding on from there once you get that working properly.