What you'll need
A USB lightning cable (the same one you use to charge your phone)
A Mac (MacBook, iMac, Mac Pro)
Step 1: Connect your iPhone to your computer with the USB cable.
Exactly as if you're connecting your iPhone to iTunes.
Your iPhone might ask you if you "Trust This Computer". Tap Trust on your phone.
Step 2: Create a new QuickTime recording
On your MacBook, open QuickTime Player, then go to File > New Movie Recording
Step 3: Switch the camera option
Your phone's screen should now be accessible in QuickTime.
In the movie recording dialogue click the small down arrow next to the recording button and choose Camera > iPhone (this should show the name of your iPhone)
Step 4: Share your screen in Engage
On the Engage website where the video is running, click the button to share your screen, so the researcher can also see your iPhone screen.