I’m sorry for those defective information on the wiki.
You can see 4 pins on the back of the FM board: D1, D2, VCC, GND.
Connect VCC to 5v, and connect GND to ground, and press the button for 3s, then the led of D1 will turn on. Just listen.
If you want to turn off the FM, press the button for 2s, the led of D1 will turn off, and board is out of power.
By the way, if setting the pin of D1 to a high level, the board will always on; set D1 to a low level, the board will always off. We will add those operation information to the wiki later. Thanks for your attention.
A few more questions . . .
Can the FM receiver be used standalone, without any other boards (as long as it is connected to power)? And in this case, is it possible to tune the station directly on the board, or do I need to attach an external potentiometer? Will the board retain the previous station setting after it is turned off and on again?