If you using SmartSense, you can adjust the sensitivity by changing the finger capacitance value. Refer Figure 5.3 in CapSense design guide.
It is recommended to use CapSense Tuner GUI (synchronized mode) to fine tune the CapSense parameters.
We have provided detailed step by step instructions on how to tune a CapSense button for optimum performance in the CapSense design guide. Please refer to that and let us know if you face any issues in any step.
CapSense design guide: Section 5.2 Manual tuning: