Without further context here, it is difficult to be certain what the question is, but it sounds like you would like to change the size of a youtube video when it gets embedded in a NationBuilder page using our embedly integration (which automatically embeds videos when you paste a youtube link into your text editor). 

Unfortunately the embedly integration does not allow for this type of control; it has a set width and height that it embeds the videos with. However, you can get around this by embedding the video directly into the template of the page instead of just pasting a link to the video in the text editor. YouTube allows you to generate an embed code (it will likely start with "iFrame") when viewing a video on youtube.com. Just look for the "Share" button and choose the 'embed' option.

You could then copy that embed code and paste it into the "Template" tab of your page using the following instructions:
http://nationbuilder.com/how_to_add_a_widget_to_webpage

The embed code includes "height" and "width" values, which you can change directly in the code there.

And if you are super familiar with HTML and Liquid coding, you can have a greater control of where that video can go in your page: http://nationbuilder.com/how_to_embed_widgets_code_iframes_between_the_content_text_or_body_text_of_a_page_or_email_blast

If you're still confused and would like further explanation, feel free to shoot us an email at [email protected]!