The video I will be using is one of the videos from the "Important Videos" playlist on Youtube.
So, you found a video you want to steal -er embed into your website. It's super simple to do this. If the uploader of the video allowed youtube to produce an embed code, you should find an "embed" button. Press that button and you'll get this menu...
Near the top of the embed menu previously mentioned, there should be a text field with some text in it. Typically the text starts with the string of code "<iframe src=..."
This is the simplest part! Just click and drag your cursor over the text in the field to highlight it. Once the entire string of code is highlighted, press and hold ctrl and c. It should be copied now! Go to the webpage you are trying to embed the video into and press and hold ctrl and v. Voila! The code to embed the video is now in your code! Congratulations!
Now, it is important to follow copyright laws when borrowing videos for your webpage. Although Youtube has designed it to make content creators still profit off of embeded videos, it is still important you respect their rights as a content creator.