At YouTube, select an appropriate Web resolution to view (usually I pick a 640 or 800 wide image if it is available), then right click the playing video and select, "Copy video URL" (shown using Chrome - currently by for the best available browser).

Then switch to the article you are posting, and:

1) Select the "Insert/Edit embedded media" icon (will only show if Javascript is enabled and working in your browser)
2) Paste the filename obtained from YouTube into the article
3) Choose an appropriate resolution (I usually will use 640 or 800 and then check "Constrain proportions" rather than entering a verticle resolution)
And bingo, you are done:
Go to YouTube, and with the video playing:

1) Select "Share"
2) Select "Embed"
3) Choose an appropriate resoluion - here 640x360
4) Make sure that, "Use old embed code" is checked
5) Copy the embeddable HTML to the clipboard
Now head over to your post:

Disable rich text, then past the embed code where you want it:

Finally, "Enable rich-text" again, et voici:
Save your post:

And bask in the warm glow of admiration :-)
Some 200 attempts are made, each and every day, to sign-up to use this site. Going on past experience, most of them, human and bot, are made in order to advertise (in decreasing frequency):
I'm not interested. I know the people who visit here regularly are not much interested either, and even if they were, I'm sure that most of them are smart enough to figure out how to use Google to find the best possible deal for the best possible product (zOMG those are beautiful shoes. OK. I'm back, distraction over.). So, nobody who matters here desires advertising crap and because of that there is no automated sign-up, no computer to fool, and in consequence it is difficult to sign-up, easy to be banned, and generally not worth wasting your time trying to figure out how to publish spam on this site.
Others apparently try to sign-up hoping to promote an agenda which is not mine, often including (in decreasing frequency):
I'm still not interested. I'm sure there are forums for you Internet trolls and your always-invalid, write-only content. This is not one of them.
Dealing with the flotsam and jetsam of the Internet on a daily basis is exceedingly boring and nobody pays me to do it so I don't. Dealing with the mess such vandals can cause when they figure out how to defeat Captcha and other bot snagging filters by putting a human spammer to work is not just boring, it is really annoying. So I don't do that either. I merely route *ALL* join-up requests to /dev/null. If you are in one of these groups, feel free to look around, see that it hasn't happened for anyone else, deduce that it isn't going to happen for you either, and go and bother somebody else. As Oscar would say, "Go Away."

If you managed to get past Oscar, and don't fit into one of the above identified categories of lamer, you might be family, a friend, or just interested, for whatever weird reasons, in having an account here. In which case, please sign-up for one using the "Create new account" page, and then send me a note telling me why you would like an account using the "Contact" page and including your user name in the message (as otherwise I won't know what you picked), and I will try to enable it for you, perhaps after emailing if I don't know who you are.
It may take some time to receive a response even after doing all this. Sorry. I am a busy person, and, while I usually do see things sent via the contact page, it is sometimes swamped by the diligent (if really stupid) people who would like to "help" me: "optimise your web site"; improve its "ranking in the search engines" or even "improve your income" - proving their idiocy by missing the point that this is merely a hopefully-slightly-less-brainless-than-facebook, strictly not-for-profit, corner of the InterTubez, where the Hermits can keep track of "stuff", stay in touch, amuse and educate family, friends and like-minded people. If you are in one of these categories, or for some unknown reasons would like to join one of them, please feel free to send me a stream of reminders until you receive a response, using the contact form - I really don't mean to ignore you. Anyone else, see Oscar and leave me alone.
Thanks
The Hermits & Co