To use it, just add the images you want to include in the composition with the 'add photo' option, plus the photo that will serve as the base of the mosaic with the 'compose' button.
Once you've chosen the second option, you can decide the final size of the mosaic, then let the application do the rest.
In just a few minutes, your mosaic will be ready. You can use it in other projects or even print it out.
Mosaic supports JPG and BMP images and exports compositions as BMPs.