When using CorelDRAWs latest version X6 you need to download the plugin manually from here.
Make sure that you select the right version and system type (32 or 64 bit). To find out which version to download between X6.1 to X6.4 please open CorelDRAW, go to the Help menu and choose About CorelDRAW. Here you will find what version you are using. For instance, this computer has Version 184.108.40.2063 installed which translates to X6.1. It's only the first two sections that are important (e.g. 16.1).
Make sure that both CorelDRAW and SignCut are closed during the installation of the plugin. Once the installation is complete you should open CorelDRAW and create a simple text and export it once manually to make sure the settings are correct for the plugin. If you are unsure of what the settings should be for the manual export you can find that information here.
Once you have done this you will be able to send to SignCut from CorelDRAW by using the option "Send to SignCut" in the application launcher in the toolbar.