This is how I removed the tail light and installed the Vizi-Tec SB-II brake light modulator on a 2013 Triumph Street Triple. I had trouble finding the correct connector, as the brake light modulator comes with the connectors pre-installed for your specific motorcycle. After quite a bit of searching I finally found out that the correct connector is hidden from view. It is located between the seat lock mechanism and the tail light.
Tools you will need:
Large allen wrench from bike
Step 1: Removing Tail Light 
The two bolts are now removed. Now you need to remove the two 8mm hex head bolts with a socket wrench.
Step 2: Removing Tail Light 
With the previous two bolts removed, you will need to pry the painted pieces away so that the grey plastic piece can be removed.
Step 3: Removing Tail Light 
Now that the plastic piece is removed, you have access to the bolts that hold the tail light on. You will again need the 8mm socket to loosen them.
Instead of removing them, I loosened them until the tail light was removed. That way it was two less bolts I had to worry about keeping track of.
Step 4: Removing Tail Light 
The tail light simply drops out. It will fall unless you support it.
Step 5: Removing Tail Light 
Now that the tail light is no longer attached to the frame, you have access to the brake light connector.
From this point you can install whatever accessory you are trying to. For me, I was installing the SB-II brake light modulator, which is a plug and play in-line accessory.
Step 6: Installing Vizi-Tec SB-II Brake Light Modulator 
From here I install the brake light modulator.
Initially I was thinking I could keep all of the connectors and the modulator tucked away in the original location. I tried to install the tail light but there was just too much extra wire and too many components that got in the way. So I uninstalled the brake modulator and fished the connector from the harness back through the frame and into the under-seat compartment.
Step 7: Installing Vizi-Tec SB-II Brake Light Modulator 
Now that the harness-side connector is in the under-seat compartment there is a lot more room to play with.
Step 8: Installing Vizi-Tec SB-II Brake Light Modulator 
I noticed there was the same size gap on the right side of the frame where I could fish the brake light modulator connector back through the frame. This made it easier to re-install the tail light.
Also, I used the connector already located in the under-seat compartment as a make shift tie-down.
Step 9: Installing Vizi-Tec SB-II Brake Light Modulator 
Since the brake light modulator and the extra connectors are now in the under-seat compartment, the tail light is much easier to install.