To create a marker icon in Leaflet, you need to create an instance of the L.icon class. The L.icon class takes 10 options, as follows:

The only required option is iconUrl. In this example, you will ignore the retina images and the class name. Open LeafletEssentials.html and add the following code:

var myIcon = L.icon({
    iconUrl: 'mymarker.png',
    shadowUrl: 'shadow.png',
    iconSize:     [40, 60], 
    shadowSize:   [60, 40], 
    iconAnchor:   [20, 60], 
    shadowAnchor: [20, 40],  
    popupAnchor:  [0, -53] 
});

The preceding code sets the options. The iconUrl option directs the URL to the icon image and the shadowUrl option directs the URL to the shadow image. The iconSize and shadowSize options require the dimensions of the images in the format of width by height.

The iconAnchor options set the point at which the marker and icon...