Log in to your Atlassian account, click on your account icon , then select "Account settings";
When your account settings are shown, select the tab "Security";
Scroll down the settings until you find "Two-step verification", then click on "Manage two-step verification";
You will now need to supply your Atlassian account password, then click 
;
Next, select the authentication method "Security key";
You will then be asked to get your security key ready - insert you Fido2 key into an available USB port, supply a name for your key, then click 
;
You will then be asked to select where to save the passkey, select "Security key", then click 
;
You are now notified that access to google will be prepared with your Fido2 security key - click 
to proceed to the next step;
You will be asked to touch the button on your key (if your model has a fingerprint reader you may be asked to provide a finger swipe instead);
Provided you press the button on the Fido2 key in the allowed time, the passkey details will be stored on your Fido2 key, and you will be presented with the following confirmation;
Click "OK", and you will be shown a list of emergency recovery keys that may be used if required (we suggest you make a note of these in the event of a lost Fido key).
The Fido2 key is now ready to be used when you next log in to Atlassian.