To install OctaneRender® on Windows, ensure that you have installed a suitable driver for your video card. After this, you only have to run the installer.
OctaneRender® v4 is a CUDA 9.1 application. It will require a current Nvidia graphics driver of version 388.x or higher.
The latest video card driver can be downloaded from here:
For Windows and Linux: http://www.nvidia.com/Download/index.aspx