Hi,
Recording the iPhone is very simple and does not require any software. As long as you have a Mac and OSX Yosemite or higher. An iPhone 5 or iPad 4 and higher. (a device with the 8 pin lightning connector) If not, update your Mac not. If you don't have a Mac you can ignore the rest of This post.
Plug your iPad/iPhone into your Mac. Open up quick time player. Click file > new movie recording. Click the arrow next to the record button and scelected your phone for both audio and video (if you want to do voiceover, scelected your phone for video and scelected your microphone for audio)
Click record