The oxygen sensor in your Suzuki Swift is a device that measures the air and gasoline mix that is coming out of the engine through the exhaust. By monitoring the exhaust, it can tell whether you are "running rich" (burning too much fuel) or "running lean" (not burning enough). It then signals the ECU (the Suzuki Swift's on-board computer) to adjust the air/fuel mix as necessary. The goal of the oxygen--or O2--sensor is to give the best fuel economy combined with good power and low emissions.
Place a small amount of anti-seize onto the threads of the oxygen sensor.
Insert the sensor into the area designated for the O2 sensor. This will be on the exhaust pipe where the old O2 sensor was located. Depending on the year of your Suzuki Swift, you'll find this above or below the catalytic converter.
Place the end of the O2 socket extension onto the O2 bung and begin tightening the sensor by turning it clockwise.
Plug the electrical connectors into the oxygen sensor's bung/housing. These wires are necessary to send the information to the Suzuki Swift ECU.
Turn on the vehicle and verify that the "check engine" light does not stay on. If you installed the oxygen sensor on your Suzuki Swift correctly, the "check engine" light will come on when you first start the vehicle, and then it will go out after a few seconds. This indicates that there are no malfunctions with any components - including the one you just installed.