How do I reduce my attack surface?

Direct proportion: Reducing attack surface means increasing security

Attack surface reduction principles include:

patching
shutting down network ports
retiring unused services
reducing the amount of code running
setting strong trust boundaries
security awareness training for employees, and more.

You can use the info from your Pentest-Tools.com Attack Surface view to gather the necessary data, prioritize actions, and then monitor if your remediation tactics have the desired result.

For in-depth information about the topic, check out this guide from Infosec Institute.