If you have not already done so, configure your browser to use Burp as its proxy, and configure Burp's Proxy listener to generate CA-signed per-host certificates (this is the default setting).
Launch Internet Explorer. On recent versions of Windows, you must run IE as local administrator.
Click the "Start" button, type "internet explorer" into the search box, right-click the Internet Explorer link, and select "Run as Administrator" from the context menu.
Go to the "Tools" menu and click “Internet Options”
Select the “Content” tab and then click “Certificates”.
Select the "Trusted Root Certification Authorities" tab.
Locate and select the "PortSwigger CA" entry in the list.
Click "Yes" in each confirmation dialog.
Confirm that the "PortSwigger CA" entry has been removed.
Restart Internet Explorer.