Open the Settings app
Tap Sounds & Haptics
Under Ringer and Alerts, drag the volume slider to the desired level
Turn on Change with Buttons if you want to adjust alarm volume using the volume buttons
Open the Clock app
Tap Alarm
Tap Edit
Select the alarm
Tap Sound
Choose a louder or softer alarm tone if needed
Test the alarm volume by setting a short alarm or using the volume slider while media is not playing