Ok I will try to fill you in.
You COPY the last message from the vine. Hit reply. This opens a reply box. You PASTE that list you copied into your new post and ADD yourself at the bottom (with the next consecutive number). POST your reply. You will get a chance to review your post to see if you need to fix it, then POST reply. Then you return to the new post to ensure all is well and you now copy the topic (title) of that vine...such as ...

Not a newbie but need a quick refresher, its been 7 years...

(You now use that when you send a PM ie private message to the guy who is preceding you on the vine.)
To do that you click on the highlighted name of the guy who posted ahead of you (over on the left margin). This opens the private message page. You PASTE the topic in the top line so the guy knows which vine you are talking about. You make a brief message then your name and address for the envelope. remember to use your full zipcode because some folks here are from outside the USA.
When you receive the package you copy the show ASAP and repackage the original discs in a suitable mailer to send to the guy who follows you. You will find his address in your PMs inbox because he followed this protocol and you already had it in your PMs from when he signed up for the vine.
YOU UPDATE THE VINE by finding it in the forum, going to the BOTTOM and COPYING the whole list. then hit REPLY. When the box opens you PASTE that list into the box. Then you find where your name is and you enter the info such as **IN 3-16, OUT 3-17**. It will let you preview it and you look for errors, if none POST REPLY.
Now you go back to your PMs and find that message from the guy who sent you his address and you reply again to his message with a quick note to tell him you just sent the vine his way.
I hope this helps. I will send you a quick pm with a fake vine so you will see a typical PM. I tried to be explicit and take you thru step by step.
ENJOY !

thank you oldblue