First, clip your breadboards together, with the longer sides together.
Then, if you have a Cobbler (see Step 1), push it into one of the breadboards so that its pins straddle the gap in the middle of one of the breadboards. Then proceed to connect the 5V, 3.3V, and ground outputs from the Raspberry Pi's GPIO to the rails on the side of the breadboard.
This is done because these are the most commonly used pins from the Pi, so they need to be easily accessible.
Then add your MCP3008 ADC to the breadboard in the same fashion. When looking at it from above, with the small notch at the top, the 8 pins on the right are connected to the Pi, and the 8 pins on the left are used as inputs to the ADC, normally coming from sensors you've placed onto your board. These are the connections which you need to make from the 8 right hand pins:
This pressure and temperature sensor has either 6 or 7 outputs, depending on where you obtain it, however this does not impact its installation, as the pin missing from some versions is not important for our usage of the sensor. Connect the pins as follows:
While holding the sensor facing you (so you can see the grating), the pins are numbered from left to right 1, 2, 3 and 4. Connect them up like this (Pin 2 is connected to two places, that's not a typo!):
To connect the LDR to your breadboard, attach one end of it to ground. Connect the other end both to 3.3V via the 2.2KΩ resistor, and to the first input on the ADC (the one closest to the notch on the left).
If you're looking at this sensor from above, with the little bump at the top, the pins are numbered 1 to 4 working clockwise from the pin directly to the right of the bump. Connect them up like so:
Using the same pin numbering as for the TGS 2600, connect the pins as so:
Using the same pin numbering as for the TGS 2600, connect the 4 pins like this:
Connect the shorter leg of both resistors to ground via a resistor each. Then connect the longer leg of the red LED to GPIO #21, and the longer leg of the green LED to GPIO #22.
Insert the UV sensor, the capacitor and the 1MΩ resistor into the breadboard so that they are connected in parallel, and then connect the whole thing to ground on one side and to pin 3 (the non-inverting input) of the op-amp on the other side. Here's a small circuit diagram:
Then connect the remaining pins on the op-amp follows: