Obviously we need to start from the beginning but just in case you do not know where to find Virtual Box, here is the official link where you can download the latest version of this virtualization software either for Linux, Mac or Windows.
Also here is the link to download the official ISO for Kali Linux, be careful and verify that the MD5 Hash corresponds with the one published on their website, sometimes harmful software may be installed in this type of ISOs so just be cautions and double check that prior the installation.
Once that you have Virtual Box Installed in your computer, open it and follow the instructions below:
Click in Add and configure the following options
Select recommended RAM memory, it will depend upon your capacity, in my case I will have 4GB assigned to Kali
Create a virtual Disk to store the information of your Virtual Machine
Select the size if your VDI disk, usually for Kali Linux you do not required more than 30GB, it depends about the amount of scripts and files you use.
Go to Settings to configure ISO and Graphics Memory and processor
Go to Storage, select “Controller IDE”, and then Choose Virtual Optical Disk File
After all this configuration, select OK and then start the VM.
You will see that it will open a new window with the VM inside, after that we have to SELECT “Graphic Install”
SELECT your proffered language.
ENTER the host name for your VM and follow the wizard configuration
AFTER this steps you will be able to see your Kali Desktop