The simplest way to attach the sensor is to use this STEMMA cable. No soldering required! Just plug it right in to the port on either side.
I didn't have a double-ended STEMMA cable on hand during the build, so I used a slightly different method using this STEMMA-to-male-header pin cable. The benefit of this was that the female header on the sensor creates a really stable way to attach the sensor in a perpendicular orientation by the money slit.
Solder your female header onto the bottom side of the sensor. Plug in the four cables into the first four header ports as shown: red to VIN, black to G, yellow to SCL, and blue to SDA.
Plug the other end into your MatrixPortal and you're ready to go.