This command activates 'vboxmanage', a command-line program included with Virtualbox that allows you to edit the properties of your virtual machine, including its built-in resolutions. Vboxmanage setextradata 'Name of virtual machine' 'CustomVideoMode1' '1920x1080x32' This command will change the focus of the Command Prompt to the program folder for Virtualbox (if you installed Virtualbox somewhere different, then change the command to wherever you installed it). Then, type the following command into the Command Prompt. You can do this by opening the Start Menu, and typing 'command prompt' into the Start Menu search bar. Next, open the Command Prompt in Windows (make sure you are logged into an Administrator account on Windows). For instance, if you want to use the 1600x900 resolution, type in '1600x900x32'. Once you've saved it, turn off the virtual machine.
You can change '1920x1080x32' to whatever resolution best fits your monitor.
