Membership Upgrade Option configuration

One of my clients wants to upgrade from a Free Subscriber status to Elite. I currently have 3 subscription levels: Free, Premium, and Elite. I will attach screenshots of how I have this set up (because I am not certain it is correct). I do not know how the client can upgrade from her end. I can obviously do a manual upgrade and send her an invoice, but would I need to create a 4th subscription level called “Upgrade”? I have created an upgrade button on paypal and can insert that code anywhere, but am I missing something?