You can turn on AdSense for a specific Blog page directly in the Website Editor:
- Click the Pages tab at the top of the editor.
- Select the Blog page you want from the list on the left.
- Click the Settings (gear) icon in the side menu.
- Open the Monetization / AdSense tab.
- Check Display Google AdSense.
- Paste your code into Google AdSense Site ID, then toggle Activate AdSense on.
- Click Save.