Locate your robots.txt file
From your Hubspot Dashboard, navigate to Content > Content Settings.
Example: To exclude all files except one
There is no "Allow" field or functionality for a robots.txt file, so the easy way to exclude files is to put all files to be disallowed into a separate directory, say "stuff", and leave the one file in the level above this directory:
User-agent: * Disallow: /~joe/stuff/
Alternatively you can explicitly disallow all disallowed pages:
User-agent: * Disallow: /~joe/junk.html Disallow: /~joe/foo.html Disallow: /~joe/bar.html
Save your changes
Click Save to finish updating your robots.txt file.