You do not need to log into your account on Shop to purchase the upgrade. Simply follow the upgrade link and use the same email address that you have registered Liquid Rhythm with, we’ll take care of the rest. If you own Liquid Rhythm, there is a discounted upgrade path for Liquid Music of just $99.99.
Once you have purchased the upgrade, follow the instructions in the email to download and install Liquid Music. Run Liquid Music in Ableton Live and input your new license in Liquid Music. It will upgrade your existing Liquid Rhythm license to a full Liquid Music license.