I assume that FO stands for Fail Over. In terms of a true active/standby failover I am not sure that you could do this on a 1941.The closest that I can think of would be to configure Integrated Routing and Bridging. In doing this you would configure both LAN interfaces with bridge groups in the same bridge group and would configure a BVI for the bridge group. You would put the IP address onto the BVI. This would allow both LAN interfaces to be active and participate in the same vlan/subnet. One interface would be active and if it failed then the other interface would forward the traffic.
I doubt that there are instructions for this model to implement IRB since it would not normally be a recommended implementation. If you would like information that would help you with configuration of IRB on the 1941 I would suggest that you begin with this link
