Connect the outputs (3,4,5,6,7 or 8) on your Digi 001 to the inputs on the RNC. Then connect the outputs of the RNC to an input on the 001 to bring the signal back. So the signal goes
Digi 001 output 3 > Input 1 RNC > Output 1 RNC > Digi 001 Input 4
Under the I/O setup name the output used...