Google adsense code in HTML

Dear There, 

Google adsense ask me to paste the following code in into the HTML of my website, right after the <head> tag. They will verify it in three days !!!

<script async src="//"></script&gt;
  (adsbygoogle = window.adsbygoogle || []).push({
    google_ad_client: "ca-pub-0000000000000",
    enable_page_level_ads: true

I am new to ELGG, where to paste it in my ELGG website?