Limiting access to features on devices such as iPads when using them for Kiosks or for use
as a Point of Sale Station requires the use of Apples Guided Access. Guided Access limits your iOS device to a single app and lets you control which features are available.
Guided access also prevents the Apple devices from being used in ways you may not intend when you are not watch such as surfing the internet or using other apps.
Guided access is very simple to setup in just a few steps
See more steps at https://support.apple.com/en-us/HT202612