This will open the Filter Gallery in a new window with the Dust and Scratch Remover pre-selected.
Step 3: Adjust the Radius and Threshold settings to achieve the look you want for the photo. Although it's not necessarily, I like to view both the Before and After images here so I can see exactly what changes are made.

click to enlarge
It's unlikely that you'll be able to use this tool to completely remove every single flaw in the photo, but you should be able to get the great majority of them.