To change the default programs for files and protocols, you'll need to open the Settings menu and go to System > Default apps.
Select Choose default apps by file type options. Scroll through the window to find the .ctfx file extension and click on the associated application on the right. A pop up will appear where you can choose an app to associate with the file type. Select ClickOnce Application Deployment Support Library
If you are using earlier version of Windows operating system, go to Control Panel > Programs > Default Programs > Set Associations. Select .ctfx extension and click on Change Program button.
Now, select ClickOnce Application Deployment Support Library from the window and click OK button.