Here is a full Video Guide & Photo Guide to get Kodi on your iPhone or iPad without a Jailbreak

Video Guide followed by Photo guide below

PHOTO GUIDE

Go to this website and choose to download Kodi 16.1 or Kodi 17.0 (18 is unstable) 

goo.gl/EsJADH

Click Install

Wait for it to load then click on it

The App then needs trusting so click cancel

Go to Settings then General then Device Management

Click on CVT MEDIA

Click on Trust 'CVT....'

Click Trust

Go Back to the Kodi App and it will work

PLEASE NOTE: If you get a blank screen exit the app then close it by double clicking home button then go back into and it should work fine. You are also doing this at your own risk.