Prepare the activation file you received:
Go to the Plug-in Panel > Menu > Activate… and browse your [Order ID]_xxx.ec file
Plug-in prompts you to restart your Adobe® Illustrator® session in order to complete the activation process.
After restart, go to the Plug-in Panel > Menu > About. The ‘Product Licensed…’ message should be displayed:
If you work with different versions of the Adobe® Illustrator® software: 16.0 (CS6), 17.0/17.1 (CC) or 18.0/18.1 (CC 2014), 32 or 64-bit you don’t need to perform separate activations on them! It works globally. For example, you can activate your Plug-in under Adobe® Illustrator® 18.0 (CC 2014) and this will automatically apply activation file to the 16.0 (CS6) and 17.0/17.1 (CC) versions as well.