The following will allow you to send input signal from the S16 to channels of the X32:

1.  Navigate to the HOME tab of the ROUTING screen.
2.  Each column represents a bank of 8 channels.  Set the Inputs 1-8 column to AES50A 1-8.
3.  Set the Inputs 9-16 column to AES50A 9-16.

With this configuration, channels 1-16 on the console will receive their signal from the 16 inputs of the S16 stage box.