How to install Linux on a macbook?
Download Ubuntu Live CD and burn it.
Install rEFIt (this step is optional, you can hold 'Alt' to select
partition everytime instead).
Use Boot Camp Assistant (it's in Applications/Utilities) to create
new partition. I allocate 5GB partition.
Insert the live CD into the drive and reboot
Hold down ‘C’ button at the black screen to boot from CD.
Follow usual Ubuntu installation step. In keyboard selection screen,
choose “macintosh”.
In partitioning screen, choose ‘manually edit partition table’.
Delete the 5GB partition just created from BootCamp. Then create the
ext3 partition at the same size. Mount it as ‘/’.
Complete the installation process. Then reboot.
If you install rEFIt, the boot menu will show up. If not, hold
 'Alt' button for a while and select the Windows partition for
 Ubuntu.


https://help.ubuntu.com/community/How%20to%20install%20Ubuntu%20on%20MacBook%20using%20live%20CD

If this doesn't work, then I'll need to know the version of Ubuntu that you have on CD. Rumor is 12.10 has network issues when setting it up. If you don't have anything newer than I'd recommend 12.04.