Instead, the film shows me the code from youtube

I Theme NEWS
Pasting the code <iframe width = "420" height = "315" src = "https://www.youtube.com/embed/OO_TVrs0rhw" frameborder = "0" allowFullScreen> </ iframe>
Following the publication I get this as text, not oasadzony film youtobe.
Do I need to install something or set?
Zamiast filmu wyświetla mi kod z youtube
Mam Theme NEWS
Wklejam kod <iframe width="420" height="315" src="https://www.youtube.com/embed/OO_TVrs0rhw" frameborder="0" allowfullscreen></iframe>
Po opublikowaniu wyświetla mi sie ten jako tekst, a nie oasadzony film youtobe.
Czy muszę coś zainstalować czy ustawić ?

Hi,

Where exactly did you paste the <iframe code? Could you provide your website URL with this iframe code visible?