Install as described above with the “sudo apt install virtualbox” command.
Then, go to “users and groups” in your system menu and check that your username is a member of the “virtualbox” group. It probably will be, following installation. But, it won’t hurt to make sure.
Then, open Virtualbox and make a note of your version number by left clicking on the “about virtualbox” option in the “help” menu.
Then select “virtualbox website” under the “help” menu and, once the page has loaded, navigate to the “downloads” section of your version of virtualbox. In that section, you will find a link to the “extension pack”, which you should click on and download and install. This allows extra functionality such as shared folders and, usb functionality and other features.
Then log out and back in to ensure that your membership of the “virtualbox” group is active.
At which point, you are ready to install your first VM