If you would like to use your security key for 2-step verification follow these steps.
Click "Security" from the drop-down menu.
Click on "2-Step Verification".
Click on "Security Key".
You can use multiple security keys for 2-step verification so choose a unique alias to distinguish between them and click "Next" button.
Insert your security key. If it has a button or a gold disc, tap it.
You have successfully added your security key. Click "Done" to go back to 2-step verification configuration.