These are Following Steps:-
Step 1: Open Blogger theme link and click Edit HTML Button.
Step
2: Click Middle of the code & Press Ctrl+F Paste " <div class='post-footer'> " tag then
enter twice and paste the Ad code above the " <div class='post-footer' > " tag. Finally, Click Save theme Button.
Step 3: Now Open any Post & Refresh the Page, You Will See The Ads.