Your Melomania Touch earphones can't be manually turned off. When you're finished using your earbuds, make sure to put them back in their case. This will disconnect them from your device and will automatically begin charging your earbuds.
If the earbuds are left out of the case with no audio or operations for 10 mins, they will power down automatically.
To turn them back on, either press one of the buttons on the earbuds or place them back into the case, close the lid and then remove them.