It is important to restrict device usage to the photo booth only. This prevents the booth from being disrupted during your events, and prevents guests from leaving the app and either accessing personal information on your iPad.
Enabling Guided Access
Your iPad comes with a feature called Guided Access that can prevent your guests from accessing other information or applications that are on your device.
To start using Guided Access:
Open your iPad settings and follow this path: Accessibility > Guided Access.
Enable the Guided Access feature and set a Passcode. Make sure to use a memorable code or write this passcode down somewhere. You'll also have the option to use Touch or Face ID if your iPad supports those.
Open your Simple Booth app, triple-tap the home or side button (depending on your iPad model) and press Start to turn Guided Access on.
The passcode you created or your Touch/Face ID will be required before you can disable Guided Access and exit the app. Once you enter the password, the Guided Access session will end.
Apple's Help Center has additional information about Guided Access if you'd like to know more or need additional help.