To enable-
ciscoasa(config)# ssh scopy enable
Then from your windows box-
pscp.exe asa921-k8.bin admin@192.168.0.1:disk0:/asa921-k8.bin
You can backup the config by doing-
copy running-config disk0:ASA112316.txt
pscp.exe admin@192.168.0.1:disk0:/ASA112316.txt ASA112316.txt
You get the added benefit of storing a copy on the device for future review.