- Signup for an account at https://pushover.net/ and login
- Click on Apps & Plugins
- Click on Create a New Application
- Enter a name, such as Server Monitoring
- For the type, choose Application
- Click create application
- Copy the API Token/Key
- From the WHMCS admin area, select Addons->ServerPing and paste your API token in the Pushover API Token/Key field.
Your customers will now be able to enable pushover notifications via an API Alert.