Download: Vboxguestadditions.iso !!link!!
If you are looking for the actual file, you do not usually need to download it separately. It is included with the VirtualBox installation. You can find it on your computer at: C:\Program Files\Oracle\VirtualBox\VBoxGuestAdditions.iso
Open the Explorer and navigate to the mounted ISO. Run VBoxWindowsAdditions.exe and follow the installation prompts.
The Ultimate Guide to Downloading and Installing download vboxguestadditions.iso
Restart your VM.
After locating VBoxGuestAdditions.iso , here's how to mount and install it on your guest OS: If you are looking for the actual file,
https://download.virtualbox.org/virtualbox/LATEST-STABLE.TXT (check version, then use below)
sudo sh /media/$USER/VBox_GAs_6_1_16/VBoxLinuxAdditions.run download vboxguestadditions.iso
The ISO is included in your VirtualBox installation. You can find it here:

