Here’s how to set up FogBugz for Windows to be accessible only via SSL (HTTPS).
See the TechNet documentation for requiring SSL:
1: Open IIS Manager and navigate to the level you want to manage. For information about opening IIS Manager, see Open IIS Manager (IIS 7). For information about navigating to locations in the UI, see Navigation in IIS Manager (IIS 7).
2: In Features View, double-click SSL Settings.
Make sure that you are at the site, application, or directory level; SSL Settings are not available at the Server level. To configure SSL at the file level, navigate to the file in Content View and then click Switch to Features View in the Actions pane.
3: On the SSL Settings page, select Require SSL.
4: In the Actions pane, click Apply.
This TechNet article covers enabling (and requiring) SSL.
Note: If you are seeing hg commands timeout with the error message “An existing connection was forcibly closed by the remote host” you should check your IIS SSL settings for the fogbugz and kiln sites to make sure that they are set to Ignore Client Certificates.