Rerun fdisk or cfdisk depending on your preference and reformat your card to actually use the full card's size. You will need to alter the numbers you are using if it left you with 4GB on the card unusued. You can use it like you said but you will need to edit your /etc/fstab to reflect the fact that there is a 3rd partition and tell it where to mount that accordingly on your system.. For example you "could" make the remaining 4GB be your home partition.
Thank you for the quick reply don – but I don’t understand how to “Rerun fdisk or cfdisk depending on your preference and reformat your card to actually use the full card’s size.”
I can run fdisk or cdisk, but don’t see how one reformats the card from those commands. As I said, I’m very new to this.
Regards,
Curt
Never mind – I figured it out I think. It took a leap of faith to delete the second partition of mmcblk0 and then add it back again at the larger size using fdisk, but it seems to have worked.
Sounds like you got it 
I did not have time earlier to dig up a link but here is a starter for you
http://www.oesf.org/index.php?title=Step-by-step_CF/SD_fdisk/formatting_for_newbies
Just google how to format a sdcard with fdisk, there a tons of tutorials 