Hold the underside of the cap, stretch the material in all directions around the hole you intend to fit, then wedge the sensor into the hole. Push upwards first and then let the material move to fix the bottom half. Adjust the material until the sensor is fully fixed. Repeat this step for all the Sensors in your desired configuration.
Since the Saline Sensors are a little larger than the Gel Sensors, it is easier to stretch the material of the cap around the Sensors than forcing the Sensor into the cap.
With the saline felt pad facing inwards, place it over the Sensor hole into which you wish to fit it. Flipping the Cap inside out, stretch the hole over the Sensor, let the material pop into place into the plastic groove. The majority of the Sensor should be on the outer side, while the felt should protrude towards the inside, where it will be resting against the scalp when the cap is in place. Repeat this step for all Sensors.