Getting Started: Receive Data

Hello newbie here,

I’m trying the The Things Network ‘Hello world’ for Arduino" and trying to recieve data. https://github.com/TheThingsNetwork/examples/tree/master/basic/autonomo/hello-world
I have two questions regarding this
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1. What do I do with the API?

2. I don’t understand what “Replace 0000AA01 with the device address you set in step 5.” means.

Could someone help me with the next steps?