Neither that links or the ebay sale mentions how it is used. It says in the link that it doesn't degrade the internal structure of the tyre, so one would assume from that that it is applied through the valve, but the bloke selling it on ebay, doesn't seem to be selling a pump adapter or any other means of getting it into the tyre.
I would imagine, being latex based, that it will cling to all of the internal surfaces and act as a flexible membrane to stop air escaping when punctures occur.