I am working on Season 6 Episode 2 and when I wound on the last green threads I only put on 8 instead of the required 13. How do I put more warp threads on now and retain a tension on my warp ? I have actually threaded the entire warp down to the last before I realized I hadn't enough threads.

Make a little warp with the extra threads, thread them as usual, tie them on with the rest, and weight them as a group—tension them by pulling from the back once they are tied on. You’ll have to play around with the amount of weight you need. If the warp is now off center, you can just readjust your reed to compensate.