Here are the proper steps to connect your Audiobox iOne or iTwo.
1.) Using a supported official Apple power supply with your iPad, connect the USB cable that is included with your iOne or iTwo.
2.) Plug the power supply brick into an electrical outlet.
3.) Plug the other free end of the USB cable to the USB "Power" port on the back panel of your Audiobox iOne or iTwo device.
4.) Using an official Apple data cable (either 30 pin or lightning, which ever came with your iPad) connect the USB end to the "Device" port of your Audiobox iOne or iTwo.
5.) With your iPad in sleep mode or awake and on the "Home" screen, plug the 30 pin or Lightning end of your data cable to your iPad.
Now you can launch any application on your iPad to enable usage with the Audiobox iOne or iTwo.
AND
Since you're running an iPad Mini 2 - the power adapter that comes with the iPad Mini may not be powerful enough. Read this article for more info: https://support.presonus.com/hc/en-us/articles/210044853-What-power-adapter-should-I-use-with-my-AudioBox-iOne-iTwo-to-work-with-my-iOS-device-
AND
If you're interested in running everything on battery to make it portable, read this other article:https://support.presonus.com/hc/en-us/articles/210044873-Can-I-use-a-portable-battery-pack-with-my-AudioBox-iOne-or-AudioBox-iTwo-and-my-iPad-
For more articles we wrote for i-Series AudioBox see this page:
https://support.presonus.com/hc/en-us/sections/201961253-AudioBox-i-Series