Hi,
You can use the Width parameter in the component properties. For the electrical gaussian generator. The width corresponds to the full width half maximum of the power. So looking at the visualizer for the electrical component that would be at 1/sqrt(2) or 0.7071. The width is also normalized to the bit period, so for a 10 Gb/s signal or 100 ps bit period the width should be set to 85/100 or 0.85.
This width is actually going to overlap with pulses adjacent to it, (if you have a sequence) so I would increase the bit rate to 20 Gb/s and then set the width to 0.425.
Hope this helps!