You go here:
Software.openSUSE.org
First as you can see you choose your CPU's architecture so you tick 32 bit or 64 bit.
THEN
You choose if you want a Live CD or a DVD or a NET install CD
THEN
You choose how you want to download it
THEN
You choose which Desktop Environment CD you want (if you choose DVD then you have one choice as it contains both desktop environments and you can additionally choose what will be installed from the beginning)
THEN
Click "Live CD KDE 4 or GNOME", if you highlight that link you will see that it points to a **********.iso file