It’s simple! Refillable floss is preloaded right out of the pack. Just tap the white top to open, pull the pre-marked string until you see a green marker at ~18 inches, trim using the notch, then floss away.
Here’s a step-by-step:
To open, press down on the white top of the floss unit to release the dispensing head. It will pop up slowly with the string already set in place.
Release the floss from the notch, and pull the pre-marked floss string until you see a green marker (it’s about 18”, which is how much dentists recommend in order to use a new area tooth to tooth).
To store, press down on the white top once again until you hear a dull click
As my dentist says, floss every tooth you want to keep.