Then as next step you have 2 choices, burn the cd or mount the iso file locally as below:

sudo mount -o loop ubuntu-9.10-alternate-i386.iso /media/cdrom0

Then we can run the executable “cdromupgrade” inside the root of the cdrom:

sudo /cdrom/cdromupgrade &

and then follow the normal upgrade process through the interface.

On upgrade complete, if you use the Medibuntu repository, you will need to update the sources used and probably to update your software versions as well.
You can find below the commands that you need to run, as stated on Medibuntu website:

sudo wget http://www.medibuntu.org/sources.list.d/$(lsb_release -cs).list \
--output-document=/etc/apt/sources.list.d/medibuntu.list &&
sudo apt-get -q update &&
sudo apt-get --yes -q --allow-unauthenticated install medibuntu-keyring &&
sudo apt-get -q update

If it is a fresh Ubuntu install, you will probably want to install the commonly used packages (or you can find the complete list of Medibuntu packages for Karmic Koala here):

sudo apt-get install ubuntu-restricted-extras libdvdcss2 w32codecs skype

if it is just an upgrade, you can run:

sudo apt-get upgrade

and that will be working things out for you.

Happy upgrade!