Crouton Build kernel headers and install Virtualbox (x86)

Greetings,

I am following these instructions on how to build the header kernel for my Chromebook, I'm using Crouton to run Ubuntu 12.04 LTS.

But i do not completely understand how to proceed through a particular portion of the instructions.

I'm on the portion after i finished running the code below.

Code:

$ cd kernel
$ vi chromeos/config/base.config

And i have changed, CONFIG_ERROR_ON_WARNING=y to CONFIG_ERROR_ON_WARNING=n

I do not know how to proceed afterwards through the terminal to enter the following codes below.

Code:
$ ./chromeos/scripts/prepareconfig chromeos-intel-pineview
$ make oldconfig

All assistance is welcomed.