Hello HandE I added a video before logging in or registering in https://tnoa.com.ar. I don't know if that's what you're looking for. 

However, if you want to add a video on the main page (after logging in), as in this image, on the right:

So you have to go to Studio-Pages-Homepage (yourURL/studio/builder_page.php?Type = system & page = sys_home) and add a raw block by clicking the blue button on the right that says "Add block".

Then you must add the code corresponding to the video in the raw block.

You click on the raw block and add the code. 

I added the following:

<style>

.bx-spl-videowrapper {

        position: relative;

          padding-bottom: 56.25%;

          padding-top: 25px;

        height: 0px;  

    }

.bx-spl-videowrapper iframe {

        position: absolute;

          left: 0px;

          top: 0px;

          right: 0px;

          bottom: 0px;

          height: 100%;

          width: 100%;

    }

</style>

<div class="bx-spl-videowrapper">

<iframe src="video url?rel=0" frameborder="0" allowfullscreen></iframe>

</div>

Regards