First of all go to Prowl homepage, register an account there and install the iPhone app on your iPhone.

Now navigate on the Prowl homepage to the Settings and copy the API-key from there (yo may need to first generate it).

Next open the Snarl settings (assuming is already installed and running of course).

Navigate within the settings to the tab "Styles", choose the style "Prowl" and hit the "Settings" button for it.

Now you get a small window where you can paste the api key you copied earlier from the Prowl homepage.

If you are behind a firewall and need to use a proxy switch to the tab called "Network" and enter you proxy settings there. Don't miss to change the switch to "Yes" to enable proxy usage.

Now close the Prowl settings window and try sending a notification to Prowl using the "Preview"-Button on bottom of the "Styles" settings tab. You should get a Prowl notification within a few moments on your iPhone.

That's it - Prowl is now configured To take full advantage of the Prowl support within Snarl just some words about Applications and Notification Classes.

Every application with Snarl support registers itself with Snarl including one or more different notification classes. So you can customize any different class to have have different timeout or different styles. And here we are back to Prowl. You most certainly don't want to have all Snarl notifications on your iPhone but only certain types. To achieve this navigate to the "Apps" tab, choose your app, it's notification class and change it's "Visual". Find below an example where the app "Weather" shall use Prowl for the "Current condition" notification class.