If you want to install Redhat, you need at least 2 partitions for Linux, one to put your files on and another for your swap space (similar to your swap/page file in Windows, but on a separate partition). You can also create additional partitions for your files, (ie. one for /home, one for /usr, etc.) but if you're new to this, just use one for all your files and it will make things simpler.
Once you're the in Redhat installer, you can either use their Disk Druid tool or use Fdisk. Make sure you have enough blank (unpartitioned) space for Linux. If you don't, you can use the fips utility (should be on the Redhat CD under utils i think) or Partition Magic to take away some space from Windows and give it to Linux.
Once you have this, you can make a logical parition for your files and give it a filesystem of Linux/ext2 (I think it's #83) and a mount point of / (you can do this after you're done w/ fdisk). Also make another partition (I think it's twice the size of your system RAM, can anyone correct me on this??) for your swap space, and assign it a filesystem of Linux swap (I think it's #82). You can also assign mount points for your Windows (FAT/FAT32) partitions so you can access them in Linux (ie /C for your C drive)
Once you do this, you should be ready to start installing files. If you don't want to use the boot disk every time to start Linux, you can add it to your Win2k boot menu easily. I don't remember the command offhand, but look in the Linux HOWTOs and look up the WinNT Boot Loader+Linux MiniHOWTO and that should give you detailed instructions. Ok hope that wasn't too confusing--Good Luck!