want to update to 1.2.0 but have a few questions

Ok, so i am trying to root this thing.. I am having a lot of trouble with the "CWM Bootable from SD Card" step as I have no idea how to do this. I downloaded what thread thread had me download, -the 2gb clockwork and the nook cwm 3028 files, but I don't get how to put this on my SD card..

any help with this will be greatly appreciated!