To use your model in ApertusVR you need to convert you parametric CAD model into a polygon mesh file or to one of the supported file formats (see below). To make this conversion you can use FreeCad software. FreeCAD is an open-source parametric 3D modeler made primarily to design real-life objects of any size. You can download it here: https://www.freecadweb.org/downloads.php.
After you have installed FreeCad you can import your model by clicking File ->Open and then choose your file from the directories or use File->Import. Click on "Export" in the File menu to export your model to another format. You can find the supported export and import formats here: https://www.freecadweb.org/wiki/Import_Export .