Using Screen Time you can get an overview of how much you use your phone and set time limits on the use of selected apps. To use the function, you need to turn on Screen Time.
Press Screen Time.
Press See All Activity.
The use for the past week is displayed next to Total Screen Time.
Today's use is displayed.
Press arrow left.
Press the indicator next to "Share Across Devices" and follow the instructions on the screen to turn total Screen Time across all of your devices on or off.
You will be notified if you've used all your assigned Screen Time. You can then choose to assign more Screen Time.
Press Ignore Limit.
Press the required setting.
Press Turn Off Screen Time.
Slide your finger upwards starting from the bottom of the screen to return to the home screen.