It is not possible to use both computer and iPad at same time or your iOne or iTwo will not be recognized by your computer because the iPad has control of the device.
If you wish to use the iOne or iTwo with your computer then remove the iPad connection from the MFi port on the back of the iOne or iTwo and use the supplied USB cable to connect from an available port on your computer to the USB port on the back of iOne or iTwo labeled PC/Mac Power.
If you wish to use the iOne or iTwo with your iPad, power must be provided separate from the computer through the USB port marked PC/Mac Power port.
To review the instructions on how to connect your iOne or iTwo to your iPad you can review that article here.
To provide power to the iOne or iTwo while connected to an iPad be sure to use the approved Apple iPad power adapter.