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Could you describe us a bit more, are you referring to Normal POST Data (method="POST"), or are you willing to implement, PHP POST Data, I am providing both methods here for you.
Normal Post Data:
From "Preferences" button from toolbar, select "Advanced Settings" tab and select "Yes" from "Send Post Data" option. Review the following screenshot.
POST Data Using PHP:
To POST Data using PHP; I suggest you to read this guide here on Sending Post Data using PHP.
I hope this helps, please will let us know further if you need more assistance we would be happy to assist you.