The way to make a GET query to a script would be something like
xfer = CreateObject("roUrlTransfer")
xfer.SetMessagePort(port) ' assuming port has already been created
xfer.SetUrl(your_url)
response = xfer.GetToString()
As for where to put it, that depends on how you wrote your code. It would be before you call Play on the video player or video screen you're using.
--Mark