OK.
Step 1. Go to the video on Youtube that you want to post here.
2. Look up at the top of your window. You should see something that looks like "http://www.youtube.com/watch?v=" and then a bunch of random characters. THIS is what you want.
3. Rapidly click three times on the bit of text that I mentioned in step 2, including the random characters at the end.
4. Hold down the key on your keyboard labeled "Ctrl" or "Control". While still holding down this key, press the "C" key. You have just copied the text.
5. Go to a new post in this topic at the Wrongplanet forums (I assume you know how to do this since you've already posted multiple times in this topic
).
6. Look for a long, rectangular blue box at the top of the posting area that has a bunch of little symbols, with "B I U" at the end of it. Look just to the left of the B and you should see a mini little Youtube logo.
7. Click on said Youtube logo. A small window should pop up that says "Enter the Video URL". Remember the text that I said you "copied" earlier? Well we're going to "paste" that text right here. So, click on the small text box below the words "Enter the video URL" and, while holding down your same "Ctrl" or "Control" button, press the "V" key. The text that you "copied" should have been "pasted" into the text box.
8. Press OK. A bunch of stuff should appear in your post, but don't delete any of it! Just keep on typing your message right after it.
9. Once you're done with your post, press the Submit button and I assure you that your video will be there!