flumixt,
let us know what distribution of Linux you installed, it'll be easier to give you detailed instructions then.
Anyway (I'm not using Linux anymore, but these informations should not be outdated), general steps are:
1. Create some free space on your HDD. Just delete partitions you don't need so it shows as "unused". Then, create two partitions - one will serve as swap partition, second as main (/) linux mountpoint. Note their sizes. I usually set swap's size 512MB.
2. During installation process you will have to specify where to install Linux, and which partition to use as swap space (actually, swap partition IS optional, but you want it). Partitions in linux are not D: or E:, they will most like be /dev/hda2 and /dev/hda3 - but I can't guarantee it, so that's where you read your notes about sizes and choose correct ones. Installer should format them with default filesystem. If asked whether you want to partition your drive - answer "no", you already have them.
3. Follow the directions
As I said, I've stopped using Linux almost 2 years ago and I have not much experience with newest distros and their installers, but if you provide more information I might be able to help more. You will also find
valuable information here.
Mike