Step-by-step: Restricted Access
Restricted Access is a feature that allows you to set which features, apps, and content your child can access. For instance, you can set restricted access for the camera to prevent your child from taking excessive amounts of selfies, and restricted access for apps to prevent your child from installing or deleted apps and making in-app purchases.
Go to Settings > General > Restrictions
Click Enable Restrictions, and set your passcode. This Passcode can be different from your iPad or iPhone passcode. Please do not share this passcode with your child.