A flash Drive or an External Hard Drive might be the easiest solution, but you can transfer the files directly through the OS. Go to the user folder of the account you want to transfer the files to, *while still in your own account*. Find the folder called 'drop box', and put all of your files into this folder. You cannot open this folder, all you can do is drag files into it.
When your done that, log into the account you just transfered the files to. Go back to the same user folder (this time inside the account) and you will be able to open the drop box folder and access all of the files.
Come back and ask questions if you can't get it, I'm not on my mac so my instructions might not be very clear.