Daisy chaining is easy.
Remember that important switch on the back of the control box? Make sure its turned on. That's on both lights. Now, decide which light will be closer to hand, and call that the control light. Plug that grey cable into hole number 2. 2 is the output Chanel and sends the commands. Here's a pic
Now on your next light, plug the other end of that cable into hole 1, the input Chanel. Again a picture
In theory (according to the instruction book) you can connect 3 of these together, putting the next grey cable into hole 2 and then hole 1 in the last light
If either light is set to less than 100% power, then that will be the highest power you can turn either light up to, so make sure any slave lights are always set to 100%. If the lights are connected, they cannot be used separately. If either light is turned off or unplugged, neither light will work.
However when both lights are set up properly, from the one switch you can turn both lights on/off, and turn them from 10% power to 100% very easily.
Here's mine, daisy chained, hanging, and running at 25% power, so that's around 75w between the two. Its nearly bed time for the plants, so the tsl2000 is off and they are on low light for their last hour.