To add a popup AdSense code to your Blogger blog, you can follow these steps:

1. Sign in to your AdSense account at https://www.google.com/adsense/.
2. Click on "Ads" in the left sidebar.
3. Click on "+ New ad unit" to create a new ad unit.
4. Select "Popup" as the ad type.
5. Configure the ad settings according to your preferences, such as ad size, style, and colors.
6. Once you have finished configuring the ad settings, click on "Save and get code".
7. Copy the generated AdSense code provided.

Now, let's add the AdSense popup code to your Blogger blog:

1. Sign in to your Blogger account at https://www.blogger.com/.
2. Go to your blog's dashboard.
3. In the left sidebar, click on "Theme".
4. Under the "Live on blog" section, click on "Edit HTML".
5. Search for the closing </body> tag using your browser's search functionality.
6. Paste the AdSense code just above the closing </body> tag.
7. Click on "Save theme" to apply the changes.

The AdSense popup code should now be added to your Blogger blog, and it will display a popup ad while readers are reading your blog.