When you launch Judoscale for the first time, you'll be prompted to install an "adapter" that's specific to your app's language and framework. In the adapter installation modal, select "Ruby" for your language and "Ruby on Rails" for your framework. If you use a job backend like Sidekiq or Delayed Job, select that here as well.
Based on your selections, you'll see exactly which gems you need to install. Once you've installed the appropriate gems and committed and deployed that change, click the button at the bottom of the modal to verify your adapter setup.
Once verified, the modal will close, and Judoscale will begin collecting throughput and request queue time metrics.
Note that autoscaling is still turned off. You'll want to review your configuration before enabling autoscaling.