The applicator should be disposed of in accordance with all applicable local regulations related to the disposal of materials potentially exposed to body fluids - usually in a sharps bin.
The applicator's needle retracts and seals automatically once the sensor's been applied, so there's no exposed sharp to handle afterwards.
Because it's still been in contact with the needle and your skin, we recommend treating it as sharps waste rather than general household rubbish: a sealed rigid container, or your local council or pharmacy sharps collection scheme where one's available.
The sensor itself doesn't contain a needle, but it has been in contact with your skin throughout wear, so dispose of it according to local guidance for electronic waste and materials with body fluid contact.
Disposal routes vary a lot by region, so if you're not sure what's available locally, your council website or pharmacy is usually the quickest way to check.