Download macOS Catalina ISO. Download cache cleaner. You have to get macOS Catalina ISO in the link supplied. In this video, I'm going to show you how to Install macOS Catalina Final on VirtualBox on Windows PC with a new method. This thorough tutorial will show how.
I am running VirtualBox version 6.0.8 r130520 (Qt5.6.3) with the 6.08 extension pack on a mac mini host with a Mojave 10.14.5 operating system.
I cloned a Mojave VirtualBox image and performed a certain OS upgrade on that guest. The upgrade succeeded and the system boots and runs, except for one problem which suggests an issue with the VirtualBox USB pointing devices when used with some newer macOS kernels. Mouse drags do not work. (Simple clicks and double-clicks do work, however.) Click-dragging in the title bar of a window moves the window about 5 pixels only. Scrollbars cannot be dragged. Tests indicate that a mouse button release event is being generated as soon as the mouse is moved even though the button is, in fact, still pressed. I have tried using both the 'USB Tablet' and the 'USB Multi-Touch Tablet' as the pointing device -- both devices behave the same. The host mini does not have a USB tablet, however. It uses an Apple USB keyboard and an Apple USB mouse (neither use bluetooth). 
Install Guest Additions Virtualbox Catalina
I am able to move windows if I enable mouse-keys and use the keypad to generate mouse events. However, after enabling mouse-keys with System Preferences I am no longer able to open the Accessibility preferences app to disable mouse-keys. I get the Apple 'spinning wheel of death' and have to force-quit System Preferences. It seems possible that this hang is somehow related to the USB tablet emulator, but I have no evidence to support that.