Get into the Html Code and add in the Video tags. also in the s tarter Video tag that is where the dimensions for the video will be added then inbetween those video tags you will put the source tag and that is where the file for the video will go.
Adding the right type or multiple types will help with people using different browsers.
Also adding in other values like controls helps the user use the video options
You first have to find the video you wannt to be in your code. then look down at the share button
Then look for the embed button
Then copy the iframe code and then paste it into the html