tu go to youtube go to a vid u like and look where it says ADRESS o WWW.YOUTUBE.COM.and click your left button.if tu did it right it will say cut copy paste.if it doesnt click the other button.always copy.then paste.
well, the way i do it is first go to youtube (it doesn't seem that tu can do this with other websites) find a video tu like there. then under the vid it should have a button that says share click it then it should have a highlighted bunch of letters right click it then copy then click 'embed a video' back here and paste. simple.
here's a misceláneo vid that i embed just to mostrar it works.