The foot brake switch is located under this rubber boot...

...slide the boot up and you will see two female spaded wires attached to the brake switch. Check the condition of these wires and connections as your problem may be here and not the switch.

Pull the wires for inspection. If all looks good proceed with removing the brake switch.

Working from the left side of the motorcycle is easier.

Looking through the frame you can see the switch. There is a 13 mm lock nut below the flats of the switch...

...reach through with a 13 mm wrench and back the nut off a turn.

Now use a 17 mm wrench on the flats of the brake switch to unscrew it. You will only be able to make a 1/4 turn of so...be patient.

At some point you should be able to unscrew the switch by hand from the right side...

Switch removed.

Save the 13 mm nut and put it on the new switch.

Test the old switch (and the new BEFORE installing) by using the Ohms on your voltmeter. I use the tone feature on mine. You should get a tone when the probes touch each contact and the tone should cease when the plunger by my thumb is depressed.

Screw the 13mm nut all the way on to the new switch.

Screw the new switch on from the right side.

Be careful as the  mount for the switch is on an angle and it is easy to cross thread the switch...take your time!

Screw the switch down until it stops.

Not a good picture but this shows the new switch in place with the lock nut in the full up position.

Hook the wires up to the new switch and turn the key on...

The brake lights will probably be "On" as the switch has not been seated enough. If "On", skip to next panel.

If the brake lights are not "On"; turn the key off, remove the wires and back the switch out 1/2 turn and try again. Repeat until they come on. If they do not...you have another problem up stream in the wiring.

Turn the switch 1/2 turn further in and reattach the wires and turn key on. Repeat until brake lights go out.

I usually orient the male spades of the switch fore and aft as it is easier to keep track of my turns this way and it is also easier to attach the wires.

When the brake lights have gone out (parking lights are on), depress the brake foot pedal and see how much play is there before the brake lights come on.

Adjust the switch in 1/8 to 1/4 turns until you are happy with the pedal travel* that triggers the brake lights.

Tighten the 13 mm lock nut, watch that you do not turn the entire switch. You may need to hold the switch with a 17 mm wrench.

Replace rubber boot and you are finished.