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- Download the module archive from the client area and extract it.
- Upload the module to your WHMCS installation.
- Go to the WHMCS Admin backend, click on Setup → Addon Modules.
- Click Activate at Invoice Notifications.
- Click Configure, enter your License Key and select Full Administrator at Access Control.
- Click Addons → Invoice Notifications to open the Addon Page.
Next, please Please read the Usage page to understand all the options.