It depends what module you are using. If you look in the JED you’ll find some modules that allow you to display viodeos, but if you proceed as below it should work:
Go to the Extensions>> module manager
Click on “New”
Choose the custom HTML module
Paste the embed code from youtube in the HTML pane (make sure to switch to plain HTML if you are in WYSIWyG mode)
Select a position to place the module in
Select the pages you want the module to show up in
Click Apply and check the results
Save if it looks good or continue working on it until it does.
If you want to be able to embed the video without your visitors seeing your trials, mark the module “Special” and login into the front end as an administrator.
Good luck
