According to the Bark website, I should be able to just install the Bark plugin, and turn it on in Growl.
I swear I had this working on another OS X installation, but isn't working now.
The steps I did:
- Install Growl from the App Store.
- Install Bark
- In Growl's preferences:
- Under "Displays"
- In the drop-down for "Default Actions"
- Select "Bark" so that a checkmark appears.