Simply go to Appearance » Widgets page in your WordPress admin area. Next, drag & drop the ‘Custom HTML’ widget to the appropriate widget area and paste your Google AdSense code in there.
no need to add it between head tags
If you already have an Adsense account approved and the blog content is within the Terms of Service for Google Adsense, then you can add Adsense to monetize it.
Moreover, once you have been approved for an Adsense account, you can also put contextual ads on other sites as long as they comply with TOS.
Be sure to monetize your site with other things other than Adsense though as it could be perceived to be a MFA (Made for Adsense) site and Google hate that sort of thing.
I had that problem too, but I had to go to my site.In edit mode then click ,I think view page source and then I had to paste it in there.
I also want to know about how can i set ads to my mangazuki website. Actually, the theme is too difficult for use and i don't know about where to put responsive ads.