From your Ambient Weather Dashboard account page click on your profile logo (top right of page) that opens up the API key down at the bottom. If one's not already created you can create one there as well.
Then Install this driver [PROJECT] Driver for AmbientWeather API into your "drivers code" section of Hubitat. Then create a virtual device and assign it that driver and click save device.
The device details page will then have sections to fill in your API key and Mac Address and such then walla it should be sending data within minutes.