When I'm watching you-tube, how do I change from small screen to large screen to fill up the screen?

Or is that possible? I don't see anything to click on that makes sense. I think I've tried them all.When I'm watching you-tube, how do I change from small screen to large screen to fill up the screen?
Click my source.When I'm watching you-tube, how do I change from small screen to large screen to fill up the screen?
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well you could have loading error on the internet page, there should be a small square button on the bottom right side of the youtube video screen, it goes from small box to large box when you hover your cursor over it, if its not there. make sure your letting the web page load completely (excluding the video) before doing anything, if it still doesnt work, try a new web browser (eg mozilla firefox or google chrome, i have heard google is a good one but i use mozilla) if you try both of those and neither works try IE latest version (internet explorer, basic windows browser)