in fireworks; when you are happy with the changes you have made you must save the images
to see all the slices that are available you have to make sure in the 'Web Layer' you can see the 'eye' (shopwing all layers)
all of the slices will be shaded in green. right click on each one and pick 'export selected slice' this slice IS an image that will be used on your site (once you've done this a few times you'll know which specific images you need and which ones you dont or you may already)
when you've got them all saved then you have to rename them to what they are referred to on the site