Virtual Box: how to increase screen resolution of ubuntu

here is a simple step on adjusting screen resolution on ubuntu on virtual box,

1st: Start Ubuntu on Virtual Box(you should have done this already).

2nd:press the right control to get out of the ubuntu,

3rd: click on the DEVICES in the top of the window(menubar of the ubuntu window).

4th: click INSTALL GUEST ADDITION or if you are inside the ubuntu(your mouse is on the ubuntu hold right-CTRL + D)
after doing this you will notice that you just mounted a CD.

5th: OPEN TERMINAL go to APPLICATION->ACCESORIES->TERMINAL

6th: go to the CDROM by typing on the terminal.
cd /media/cdrom0
then hit ENTER!

7th: check the files in the directory. by typing
ls
you will see the mounted cd's directory

8th: look for the file VBoxLinuxAdditions,
as you notice this you notice other VBoxAdditions, because you can use VBOXADDITIONS on ther operating system e.g windows.

9th: now run the VBOXLINUXADDITION. type
sudo sh ./VBoxLinuxAdditions.run
on linux you can run VBoxLinuxAddition-amd64.run (or other because its you own pc setup) it will run a script. then wait until its finished

10th: now RESTART! or use a shortcut. CTRL+ALT+BACKSPACE!

final step: log on to ubuntu then go to SYSTEM->PREFERENCE->SCREEN RESOLUTION
there you can see additional resolution options, be free to use you imagination on which resolution you heart wants. :) happy learning.