Incase you do not know many bloggers on the
platform are currently using the new themes due to
the responsiveness as it adjust to fit any device.
Wow great!

Here is a very brief and comprehensive guide on
how to add adsense code below post titles on new
blogger theme.

First of all, always have it in mind that you can not
just insert AdSense code in the body of your
blogger without parsing the code.

Ok now, parse your AdSense code here before
proceeding to the next step.

=> Sign in to your blogger dashboard, Select Theme
and then click on Edit HTML

=> the next thing you need to do is to search for
this code <!-- Footer bylines -->

To view the search box where the code is to be
pasted, simply point your mouse inside the HTML
box that contains codes then click Ctrl+F then
paste the above codes and click on Enter.

=> Note that You will find more than three of such
codes after clicking the Enter button. What you
need to do now is to look for the third one and
place the parsed adsense code above or below it.
Also, you can as well place your parsed adsense
code above or below <div class='post-bottom'>.

Finally, do not forget to click the save button when
you are done.

Enjoy!

Source: http://www.johntechservice.com.ng/2017/03/adsense-code-below-post-titles-on-blogger.html