You have two options to get the plugin installed on your blog:
- Upload the knoxpayments-wp.php file itself to example.com/wp-content/plugins/
- Use the .zip file contained in the source and navigate to the plugin management page, and click the add new button next to the Plugins header.
After you do that, activate the plugin in the plugin maintenance page, and navigate to Settings -> Knox Payments.
Upon arrival at that page, fill out the API Key, API Password, the custom text you want to appear on the button, the recurring field, show all, description of the payment, and finally the callback url.
Save the changes, use the shortcode knox anywhere in your blog, and then your blog is integrated with Knox Payments!
The user is able to decide the amount to pay by default, if you want to set a specific amount use the shortcode simply provide the amount to the shortcode likes this: [knox data_amount='10'].