Control Ws2811 leds with an Ipad and HY ministm32v

You connect GND->GND, RX to TX (and vice versa), and 5V to the bluetooth dongle's VIN (it's designed to run from 5v, not 3.3v).

I'd use B10 and B11. You need to choose two pins from here that have the same USARTx part, have nearby numbers (5/6, 8/9, etc) and that don't have a pink tag next to them (which would show that they're used for something else).

Then, if it were B10/11 you'd do:

Serial3.setup(9600, {tx:B10, rx:B11});
Serial3.on('data', function(d) {
  print("Got "+JSON.stringify(d));
});

And you then just need to write some code to interpret the values that you get.