Wireless sensor networks greatly benefit from simulation before deployment, since some of these networks may contain thousands of nodes. The new challenges compared to traditional computer networks led to several approaches for network simulation, namely SENSE –– Sensor Network Emulator and Simulator. However this approach presents a limited user interface, namely based on text, forcing users to have knowledge on C++ programming language. This paper presents a tool, called G-Sense, that greatly improves SENSE user friendliness, with graphical input of simulation parameters, save and load simulation features, and simulation results management with plot view. This new tool uses SENSE simulation engine in a transparent way, so the user may be focused on the simulation itself, not in the underlying simulation tool. We present G-Sense architecture, usability and extensive experiments for its validation. We believe that this tool will contribute for SENSE adoption for wireless sensor network simulation, clearly improving on its ease of use.