In order to enable IP control of your Onkyo/Integra Receiver/Preamp you need to press SETUP button on the remote or the front of the device. When in the SETUP menu, go down to HARDWARE and then NETWORK menu item. In the NETWORK menu, make sure that CONTROL is set to ENABLED. In newer models, Onkyo/Integra added NETWORK STANDBY menu item, which as to be set to ON in order to power on the unit from Standby.
You need to make sure that the IP address of the device will not change for proper trouble free operation with iRule. You can do so by either setting the IP address static inside the unit itself or by doing a DHCP reservation in your router.
In the iRule builder you will need a device called "Integra Pre/Pro TCP Zone 1" when searching for Type=Receiver/Preamp + Vendor=Integra.
In the app, you will need to setup a NETWORK GATEWAY with IP address of the Integra/Onkyo unit and whatever port you setup in the device (default is 60128).