You don’t need to configure anything with Internet Explorer. Basically, if Foxit PDF Reader is installed,Internet Explorer is able to detect the plugin and calls it to display PDFs.
Regarding Foxit PDF Reader configuration, make sure the following things:
1. Foxit PDF Reader Plugin has been installed. Normally, it was installed by default. To check, look into C:Program files (x86)\Foxit Software\Foxit Reader\plugins, see if there is a DLL file named as “FoxitReaderBrowserAx.dll ".
2. Associate Foxit PDF Reader Plugin with Internet Explorer. Open Foxit Reader, navigate to File > Preferences >File Associations > Advanced > check the option "Include browser when setting default PDF viewer", click on OK to close the 'Advanced' window and click on "Make default PDF viewer" and hit OK button to apply the change.