KaiOS is a small operating system which isn't typically like a Linux distro which you are probably more familiar with. As a result it won't come with an installer or come on an .iso which you could load as an image into VMWare.
The KaiOS site documentation shows you how to boot the OS via PXE, which you could do with VMWare although would need to set up a PXE server VM as well as another VM which you would boot via PXE from the server you set up.
You won't be able to traditionally install this OS via loading an image unfortunately.
There is some documentation on PXE with VMWare here.