First, you will need to get space on your harddisk! Partition magic can resize NTFS partitions and I have heard that Yast2 (the setup-tool of SuSE) does that too (but I have never tried).
Once you have free space on your harddisk, yast will recognize it and provide a partition-proposal (mostly with 2 new partitions, one large for the OS, the other as swap partition). Just check that yast does not want to use the whole disk for Linux, if you do not want to get rid of windows.
Yast should then automatically create a dual-boot system, using grub as bootloader. The windows partition will be mounted read-only if it is NTFS.
That should be it ! Have a lot of fun !