On Bluetooth
The volume is normally synchronised between your speaker and your Apple iOS device or Android device. If not, you may need to enable this in the Bluetooth settings section on your mobile device (if this option is available). For more information, please refer to the manufacturers guide for your mobile device.
On Wi-Fi
You can adjust the volume directly using the controls on the speaker or by asking Alexa. For example, "Alexa, set volume to level 5"