The storage volume can be encrypted during setup. If you have already created the volume then you will need to backup your data and recreate the volume again from Control Panel > Volume.
Note: Once you have encrypted the volume, you will need to enter the encryption password every time when Amber is booting up. If you forget your password, data stored on Amber will not be retrievable. To remove encryption, you will also need to delete the volume and recreate it again.
After you have deleted the volume, click Create.
Check Encrypt this volume and enter a password.
After the volume is created, restart Amber.
After you login again, Amber will ask you for the volume decryption password.