In Pictures: How to Clean and Retouch Old Photos w...
7. Next select the raster layer. Move the cursor to the affected area and click the left button. Repeat this as many times as is necessary to paint the source pixels on to your new layer. In the screenshots we’ve shown above it appears as though the scratch and the discolouration are disappearing.
In Pictures: How to Clean and Retouch Old Photos with Paint Shop Pro