Yes, the node version is slightly outdated. The official node website does not have binaries for nodejs past version 10.
Make sure the network you intend to connect to also emits on the 2.4Ghz band. First connect to the PI using a screen and keyboard, type sudo raspi config to go into the pi config tool, enter the wifi SSID and password, enable SSH, then reboot. You should be able to connect to the Pi over SSH now. To find the Pi IP address, connect it on the network and scan the network using arp-scan. On a mac, you can install it in brew. Then sudo arp-scan --localnet. This command may show the Pi 3 times as duplicates. Just grab the IP. User/password will be the default: pi/raspberry
npm install
You can either develop on the Pi using command line tools, or on your machine with your IDE and upload it to the Pi with scp.
The DHT22 has 3 ports: VCC(+), Data(out) and GND(-)
Connect the VCC to the 3.3v pin on the PI (pin 1) Connect the GND to any ground pin on the PI (like pin 6) Connect the Data to the GPIO 4 (pin 7)
When holding the board face up and the pins are on the right side, the pins are numbered from 1 to 40, left to right, down to bottom. Here are some of their functions:
Pin 1 and 17: 3.3v
Pin 2 and 4: 5v
Pin 6, 9, 14, 20, 25, 30, 34 and 39: GND
Pin 7: GPIO 4
Pin 11: GPIO 17
You can find the full pinout diagram easily on the internet
The program connect to AWS IoT (given you provide the certificates, endpoint, and thing name), then reads a connected temperature/humidity sensor every few seconds. The exercise is to make a successful connection to AWS IoT and publish the data.