Help with wordpress and W3c Validation

Hi

I am quite new to wordpress been working with it for a week now without any experience in css and php programming but i am managing and my site is already up

https://www.portoeseautomatismos.pt

now i would like to have the site validated on w3c because the errors it is giving me are small html errors
like this:
Line 80, Column 11: Element hgroup is missing…
now what i am very confused it how w3c “reads the site” how can i find Line 80 and in what file?
On old html basic i would simply open index.html and search for it but on wordpress i cannot seem to find the exact location.

can someone give me a hint on how this works?

thanks alot