Open up the HMTL file that you want to embed your video in.
Open up Youtube or any other video service that has the video you want embedded into your webpage.
Find the video you would like to embed into your webpage.
Hit the "SHARE" button underneath the video and in between the "Dislike" button and the "SAVE" button.
After hitting the "SHARE" button, click on Embed and copy the code.
Paste the code into your HTML file.