So to use this with uart you have to install RealTerm Serial Capture. And set it up like this:

Select the COM port of your uart, and set the baudrate to 9600. Make sure your uart is set to the same baudrate in the device manager. Should be 9600 by default, but just in case. They need to operate on the same baudrate.

Connect the uart and YS-irtm like this:

Now, assign the right baudrate for the YS-IRTM(should be 9600 from default)

So now we are ready to receive the code from the remote. LG remote in this case:

So the code we received was 04 FB 12. But to output code from the YS-IRTM we have to send the "start" bits A1, F1 first. So the code will look like; A1 F1 04 FB 12

Or you could send it as numbers using; 0xA1 0xF1 0x04 0xFB 0x12

And for the arduino:
Connect the arduino TX (pin 1 on UNO) to RX on the YS-IRTM
Connect the arduino RX (pin 0 on UNO) to TX on the YS-IRTM
and ofcourse:
5v -> 5v
gnd -> gnd
Receiving code from remote. In this case LG remote controller.
(Yes, it will flash the LED every time it's receiving something)

int incomingByte = 0; // for incoming serial data
void setup() {
Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}
void loop() {
// send data only when you receive data:
if (Serial.available() > 0) {
// read the incoming byte:
incomingByte = Serial.read();
// say what you got:
Serial.print("I received: ");
Serial.println(incomingByte, HEX);
}
}
Sending code from the arduino to YS-IRTM every 5 seconds, as an example:
(Yes, the YS-IRTM will blink every time a successfull code is sent)

uint8_t my_serial_bytes[5]={0xA1, 0xF1, 0x04, 0xFB, 0x12};
void setup() {
Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}
void loop() {
Serial.write(my_serial_bytes,sizeof(my_serial_bytes));
delay(5000); // delay 5sec
}
So the code you receive will always be without A1, F1 because these are only used for the YS-IRTM to "start" sending the next bits.
Baudrates:
01 - 4800
02 - 9600
03 - 19200
04 - 57600
A1 F3 02 00 00 = set baudrate to 9600
A1 F3 04 00 00 = set baudrate to 57600
and so on..
Sending:
A1 F1 xx xx xx = Send xx xx xx
ex. A1 F1 04 FB 12