Set up an ads.txt file
If your blog is monetized with third-party providers or you’ve manually integrated AdSense in your blog, you will need to manually set up the content of the ads.txt file.
- Sign in to Blogger.
- In the top left, click the Down arrow .
- Click the blog you want to set up an ads.txt file on.
- On the left, click Settings.
- Under "Settings," click Search preferences.
- Under "Monetization," find "Custom ads.txt" and click Edit.
- Click Yes.
- Copy the settings from your third-party monetization provider and paste them in the text box.
- Click Save settings.
- Optional: To check the content of your ads.txt file, go to http://
/ads.txt.
Note: If your blog is not monetized, or it’s only configured to use AdSense using the Blogger-AdSense integration, then you do not need to manually set up ads.txt. Blogger will do this for you. Read more about ads.txt for AdSense.
reference has been taken from https://support.google.com/blogger/answer/1269077?hl=en