Welcome to the tutorial on how to install and use VirtualBox!

Step 1: Download VirtualBox

Download VirtualBox. Navigate to https://www.virtualbox.org/wiki/Downloads to download VirtualBox. VirtualBox is offered for multiple platforms, but today we are using Windows 10. Download VirtualBox for Windows by clicking "Windows hosts." When prompted, save the file.

Step 2: Download Ubuntu

Download Ubuntu. Navigate to https://ubuntu.com/#download to download the Ubuntu disc image. You may either choose Ubuntu Desktop or Ubuntu Server, whichever best suits your needs. LTS stands for Long-Term Support, so downloading the LTS version of Ubuntu will ensure that the version you have downloaded is supported for at least two years from its release date.

Step 3: Install VirtualBox

Install VirtualBox. Open the installer file that you downloaded in Step 1. All default settings should be appropriate for this task -- you do not need to change anything. Click 'Next' for every step. If you are presented with 'Warning: Network Interfaces,' check that you have no currently pending downloads or online operations, and click 'Yes.' Click 'Install' when ready to begin. This process will take some time to complete. You will be prompted to open VirtualBox when the installation has completed.

Step 4: Create Your VM

Create the Virtual Machine. Now that the Oracle VM VirtualBox Manager is installed and open, it is time to create the new virtual machine. Click the blue starburst symbol in the upper right toolbar labelled 'New.' You will then be prompted to name your new Virtual Machine. Name your VM 'Ubuntu,' and VirtualBox will automatically configure to settings to prepare an Ubuntu VM. Click "Create."

Step 5: Start Your VM

Start your Virtual Machine. Click the green right-pointing arrow icon in the upper right toolbar labelled 'Start.' This will start your virtual machine. You will be prompted to selet a startup disk. Click the small folder icon to the right of the dropdown box to choose a virtual optical disk file. Here, you will want to select the .iso for the version of Ubuntu that you downloaded earlier. Now, your virtual machine will start.

Step 6: Install Ubuntu

Install Ubuntu. If you are installing the desktop version, when your VM has booted (and this may take a while!), you will be prompted to try or install Ubuntu. Select your preferred language from the menu at the left, then click 'Install Ubuntu.' If you have ever installed Ubuntu or a similar flavour of Linux distribution before, the following process will be familiar to you. Select your preferred keyboard layout. Because we are installing Ubuntu into a virtual machine, there is no need to partition the virtual disk.
If, however, you are installing the server version, you will be prompted with a GUI-less installation screen. The server version of Ubuntu offers many different customisation options, but all defaults should be acceptable here. Use your keyboard to navigate through the prompts.