Samsung Galaxy A02s Manual Del Usuario página 5

Step 2. Turning your phone on/off
To turn your phone on, press and hold the Side key.
NOTE: The first time you turn on your phone, you will need to activate it.
See the Activate your phone guide included in the box.
To turn your phone off, press and hold the Side key and follow the
onscreen instructions.
Locking/unlocking your screen
To turn on your screen, press the Side key. Then swipe up on
the screen to unlock it.
To turn off your screen and prevent accidental key presses, press the
Side key.