PreSonus doesn't officially support the 44VSL on the iPad but it will work if you have the right connections.
You'll need Apple's Camera Connection Kit (CCK) and a powered USB hub. Note that the powered hub is needed even though the 44VSL requires its own external power supply. Connect the 44VSL to the USB hub and then connect the hub to the CCK. The CCK comes in 30-pin and Lightning styles so get the one that matches your iPad. Try not to use an extra adapter to go from 30-pin to Lightning if you can help it.
Your iPad won't get any charge so make sure that the battery is already charged up before you start a session.
Also, if you're using Capture Duo then you'll only be able to record two tracks.