We understand that it can be a little bit unnerving the first time you purchase a new plugin that doesn't come with any kind of physical installer and all you have is a license code you received through an email. In fact, 95% of audio software is now delivered electronically, so here's how to get your Waves plugins registered, installed, and activated!
Step 1: Create an account on the Waves site and log in - https://www.waves.com/create-account
Step 2: Once logged in you'll click on Register New Products and paste the serial number you received via email, eBay Message, etc.
Step 3: You'll then be able to install and activate. It uses a tool called WavesCentral that does the whole download, installation, and activation for you.
Additionally, here's the step-by-step for WavesCentral to get you up and running - http://www.waves.com/support/activate
There's even a video guide at the bottom of that page!
Time to install and enjoy your new plugins!