Assuming it's an S32, you will connect a network cable from A on the mixer to A on the stage box. In the routing tabs, you need to go to the HOME tab if you are running 3.x.x firmware and for each desired input bank select the AES 1-8, 9-16 et all. On the OUTPUT tab, you will do the same thing. AES 1-8, 9-16, or if you need some outputs at FOH you may have to get trickier.
If you are on firmware 4.x.x you will scroll to the INPUT tab in the Routing menu and do the same thing as before. Select AES 1-8, 9-16 et all. The outputs are a little more involved, but you will scroll all the way to the right to the PATCH POINTS tab and do pretty much the same thing as before where you select the desired output and where it will derive from. You can also, if you wish, do all your patching from the USER tab. Here you can select input and output sections and select 1:1 where the signal is coming and going from.
The S32 stage box may also require a firmware update? The only way to know is to connect it via USB to a computer as per the instruction in its manual. There was a recent update in 2020. V1.8 I believe? In either case, it is usually that the user didn't apply the inputs as being AES. In the X32 family, you have to tell it where you want the source to come from in a separate menu. This will then allow you to actually see that signal when you select it from the channels input source selection tab. Unfortunately, you cannot just go straight to the input channels tab and change the actual sources from there. You can select them, but the actual change to make it happen must occur in the routing menu.