Although, you can edit the settings of the alarms but if you prefer to create a new alarm, you can delete the default alarms with ease.
==> Click on the “Apps” icon on your Tecno M7, tap the “Clock” app
==> Tap on the alarm button at the bottom-left corner of the screen as highlighted below:
==> Touch and hold the alarms you want to delete.
==> Once selected as seen in the screenshot above, tap the “delete” icon.
Hope it works for you.