This driver uses the PurpleAir API to provide the air quality as reported by a selected sensor or by averaging the reports from sensors in the area you choose. There is a deprecated PurpleAir access method which some older drivers used, but I didn't see anything yet that uses this newer access method.
To begin using this driver you will need a free API key from PurpleAir which can be requested by sending an email to email@example.com.
Once you have your key just enter it and the driver will fetch all of the AQI reports in your area and report the average of them. The default search area is a square that extends 0.5 miles from the position reported by your Hub.
Alternatively, if you would like to choose a specific device to monitor you can find a device on map.purpleair.com and enter the device index. The device index can be found by selecting the device on the map and then looking for "Select=INDEX" in the URL. Currently only one device can be selected.
Below is the driver, please let me know if you have any questions or issues.