The Lightwave Link uses a different mobile app to the Link Plus and works on a different system. Therefore this means that if you have an existing Link, you will not be able to simply change across to a Link Plus. However, all devices are compatible with the Link Plus and you can keep the same credentials for your account.
On the Link Plus app, sign in with the same email and password and you will then be required to input the cloud number from the Link Plus, following that you will then have to pair your devices.