Install the toe boards in place as they are meant to be snapped on for prefabricated cabinet sets. These are usually cut to fit which means you shouldn’t need to do anything other than install them in place. The back sides of the boards have clips that attach to matching clips on the legs of the cabinets underneath the toe kick area. Snap them in place to install them.
Make your own toe boards for a custom finish. Purchase toe boards from your home improvement store and cut them to fit around the bottom perimeter of the cabinets. Mark them with a tape measure and pencil and cut them on a miter saw. Dry lay everything out on the floor so you can come back and install things quickly and easily.
Attach your finish nailer to the air compressor and let the compressor fill. Apply glue to the legs of the cabinets that extend down to the floor and press the toe boards in place. Press the board firmly against the legs of the cabinet and use the finish nailer to nail the boards in place along the legs with finish nails. Use at least one nail for every vertical inch of space along the toe boards.