The process is slightly different depending on whether you're using the Paddle or Mac Appstore version of PeakHour.
This will completely remove your PeakHour settings, including your license (if you purchased via Paddle) and your history data.
To reset your configuration, follow these steps:
Copy and paste the following and hit Enter.
rm ~/Library/Preferences/com.digitician.peakhour.plist rm -r "~/Library/Application Support/PeakHour" rm -r ~/Library/Containers/com.digitician.peakhour