If your Luxul router shipped pre-enabled, you can use the automated activation system. In the event yours is not enabled, you'll need to enable Router Limits from the UI.
Go to Firewall/Security and then Parental Controls. (NOTE: on newer firmware versions, Router Limits is listed under the "3rd Party" tab.)
The router will provide you a Pairing Code that you will need to Activate your router on Router Limits. Copy this number to your clipboard or write it down.
At this point, you can activate your router using the automated activation system.