(Note: these instructions were tested on a Windows 10 machine. Instructions might vary slightly for other operating systems.)

I. Install VirtualBox

VirtualBox is software that enables your computer's operating system (the "host" OS) to run another operating system (the "guest" OS) inside it.

 1. Go to the VirtualBox Downloads page: https://www.virtualbox.org/wiki/Downloads

 2. Under "VirtualBox 5.1.14 platform packages", find your computer's OS (Windows, OS X, or Linux) and click on it. This will download an installer file.

 3. Run the installer file (e.g., by clicking on it). Accept the installation defaults and click "Install".

II. Create a new Ubuntu VM in VirtualBox

These steps create a virtual machine within VirtualBox that runs the Ubuntu OS (a variant of Linux).

 1. Run VirtualBox and click "New" in the upper left corner to create a new VM.

 2. Give your VM a name (e.g., "COMP 115"), select "Linux" for the type, and select "Ubuntu (64-bit)" for the version.

 3. Accept the default memory size--you can change it later.

 4. Choose the "Create a virtual hard disk now" option.

 5. Accept the default "VDI" hard disk file type.

 6. Accept the default "Dynamically allocated" storage option.

 7. Accept the default file location and size (8 GB).

 8. On the left side of the VirtualBox window, you should now see a button with the name that you chose for your VM 

III. Download an Ubuntu OS image

The next step is to download a file that contains the core of the Ubuntu OS.

 1. Go to the "Download Ubuntu Desktop" web page: https://www.ubuntu.com/download/desktop

 2. Click on the "Download" button on the right.

 3. Scroll to the bottom of the next screen and click "Not now, take me to the download". This will download an Ubuntu image file. It might take a while.

IV. Configure your VM to use the Ubuntu image

These steps tell your VirtualBox VM to use the Ubuntu image file that you downloaded.

 1. In VirtualBox, select your new VM and click on "Settings" at the top of the window.

 2. Click on "Storage" on the left. Click on "Empty" under "Controller: IDE". Click on the CD icon to the right of "Optical Drive" and select "Choose Virtual Optical Disk File".

 3. In the window that appears, navigate to the Ubuntu image file that you downloaded, select it, and click on "Open".

 4. Click "OK" in the VirtualBox Settings window to close it.

V. Install Ubuntu on the new VM

  1. In VirtualBox, select your VM and click on "Start" at the top of the window. This will open a new window for your running VM.

 2. In the VM window, click on "Install Ubuntu".

 3. Check the "Download updates while installing Ubuntu" box and click on "Continue".

 4. Select the "Erase disk and install Ubuntu" option and click on "Install Now". Don't worry, this doesn't erase the host computer's contents--all of the action is happening inside the VM.

 5. Click on "Continue" in the pop-up.

 6. Enter your location and click on "Continue".

 7. Select your desired keyboard layout (the defaults should be fine) and click on "Continue".

 8. Enter your name, the computer's name (this shouldn't really matter), a user name, and a password. Click on "Continue".

 9. The VM will finish installing Ubuntu. This will take a few minutes. When it's finished, click on "Restart Now" in the pop-up that appears.

 10. You should now see a login screen (if you don't, try going to the "Machine" menu at the top of the screen and selecting "Reset"). Log in with the password that you chose earlier. Your VM is ready to use!

VI. Install MonetDB on the VM

 1. Create a file called /etc/apt/sources.list.d/monetdb.list

 2. Save these two lines in the file:
 
    deb http://dev.monetdb.org/downloads/deb/ xenial monetdb
    deb-src http://dev.monetdb.org/downloads/deb/ xenial monetdb
    
 3. Open a terminal (Ctrl Alt t) and issue this command to install the MonetDB GPG public key:

    wget --output-document=- https://www.monetdb.org/downloads/MonetDB-GPG-KEY | sudo apt-key add -

 4. Run this command to update your Ubuntu installation and install MonetDB:

    sudo apt-get update

 5. Run this command to install MonetDB/SQL

    sudo apt-get install monetdb5-sql monetdb-client

 6. To confirm that MonetDB was installed correctly, run the following commands and make sure that they output version information (not an error message):

    monetdb version
    monetdbd version

VII. Install Postgres

 1. Open a terminal in your Ubuntu VM and run the following command:

    sudo apt-get install postgresql

 2. To confirm that Postgres was installed correctly, run the following command and make sure that it outputs version information (not an error message):

    psql --version