There is really nothing to configure. The routers will actually load balance on their own as long as it is installed on both routes. It will do this if both routes are equal to each. EIGRP will install two routes going out both interfaces, as long as the bandwidth,delay,etc are equal; the routes will be considered equal. The only thing you will have to do is turn off fast-switching so that it will load balance on a per-packet instead of per-destination basis. To do this just use the "no ip route-cache" commands on the interfaces.