Below is a quick and easy guide for changing the DNS setting son your iOS device. You can only change DNS settings when you are connected to Wi-FI.

• Open Settings on your iPhone or iPad
• Select Wi-Fi
• You will now see a list of currently available networks. You should already be connected to your home Wi-Fi network so just click on the name of it
• You should now select the Configure DNS section
• To choose your own DNS you can now click on Manual
• The default dns server will already be there so click on Add Server to add your own
• Type in the DNS IP e.g 1.1.1.1
• Now click Save located in the top right corner

And that is all you need to do

Source: Kodi Addons