1. First, you want to go to your favorite video hosting site and click on your desired video.
2. Then, you want to click the "share" button under the video and click "Embed"
3. After clicking the Embed button, the source code for the video should show up: click "Copy" in the bottom right corner to copy that code
4. Next, paste that code into your HTML code, preferably into a div. You can change the height and width to 100% so they can be changed in the CSS sheet appropriately
5. Lastly, you have to adjust the dimensions in your css code in order to make sure it fits the 16:9 aspect ratio that videos have
6. At the end, it should look like this: