Quote Originally Posted by red
Do you mean after the first 3 caps, reading the layout left to right, and in parallel with the 4th cap? The kit comes with a green 5W 470 5% resistor there.
To clarifiy:looking at the first photo on this page:

http://www.tubeampdoctor.com/newsdes...newsdesk_id=40

To put in a screen grid resistor, go to the eyelet for the second cap from the left, the one where the green and brown resistors are. You would solder in the end of a 470 ohm 2-5W resistor there (in addition to the two already there) and solder the other end to pin 4 on the 6V6 tube socket.