The link starts with otpauth://, which will likely do nothing on desktop. Either click on it from a mobile device, or on desktop you can use an addon like Offline QR Code Generator (Firefox), then right-click the link and select QR code from link. This will show a QR code you’ll be able to enroll in any TOTP app. Hopefully they’ll add an option to display a QR code when using the desktop interface in newer versions of Lemmy.