To put your phone in Do Not Disturb mode, follow these steps:
iPhone:
Open Settings
Tap Focus (or Do Not Disturb on older versions)
Toggle on Do Not Disturb and customize settings for calls, notifications, and scheduling
Alternatively, you can:
Swipe down from the upper-right corner (iPhone X or later) or up from the bottom (iPhone 8 or earlier) to access the Control Center
Tap the crescent moon icon to enable Do Not Disturb
Android:
Open Settings
Tap Sound & Vibration or Notifications
Select Do Not Disturb and toggle it on
You can also customize who can reach you and any exceptions
Alternatively, you can:
Swipe down from the top of the screen to open the quick Settings Menu
Tap the Do Not Disturb icon (often a circle with a dash) to activate it
These steps may vary slightly depending on your device model and software version.