To upload video to the site, make sure you allow the file extension type, under host settings / other settings.  If you are not using third party modules, you can paste in the script or html code within Text/HTML, or  possibly try the Media Module (I haven't tried the Media Module).    However, there are some very good third party modules out there that make the process much easier, depending on what you are trying to achieve.    

If you want to change the page that is your home page, redirecting visitors to a different page as they arrive, you can change the setting under Admin/ Site Settings/ Advanced Settings / Page Management... and select the page you wish to use.