How to add legend and extent frame to the map.
[1] Now I can just export legend out as a image, but I would like to add it directly on corner of map.
[2] I cannot add extent frame (latitude and longitude ) to the map
Anyone could help me?
Thank you in advance
These GIS functionalities are not well elaborated in SNAP. Because SNAP is not a GIS software. There are other tools which are intended for such tasks and can do it better.
For a latitude and longitude grid, you can select the graticule 
from the toolbar. Afterwards you can configure the style in the Layer Manager. But probably this will also not give satisfying results.
As a workaround for the legend: You can export it to a file and then import this file as an image layer.
Thank you very much for your reply. Maybe QGIS is better to make maps and add various objects.