As soon as you connect your iPhone/iPad with the Camera adapter, you should be already good to go, since the USB1/2 are passing through the Helix signal, no matter your path settings. Just be sure your iOs device streaming icon is showing the Helix connection (look at the picture, on the bottom/right side).
At this point you can also route the iPhone to all the USB channels 1/2 - 3/4 - 5/6 - 7/8, if you have a bus app like AUM or AudioBus 2. If you use those channels, from 3 to 8, you need to set those inputs in the Helix patch, as you do with any other input source. But again, USB 1/2 are working out of the box just linking the device through USB.
Be aware that your only way to control the volume coming from your iOS device it's in the global settings, first page (USB 1/2 Trim), so just take care of your ears. ;)
PierM's post in Connect Iphone to Helix via Camera Adapter was marked as the answer