Guidance Request on Basic Serial Communications to PC

I'm a newbie working with the Arduino Uno and am looking for guidance on a Libary and direction on studies on how to accomplish in coming to PC serial requests connected to Uno through a FT232RL 3.3V 5.5V FTDI USB to TTL Serial Adapter.

Accomplished so far: Established outgoing coms from PC running XOJO via USB to TTL converter connected to Tx/Rx to control output ports, steppers, servos, LEDs, etc from a program on Mac called XOJO. Observe temperature data in the serial monitor. So far so good.

Need to Understand: How to make serial information, such as a temperature readings available at the Tx/Rx pins so Mac running, XOJO can read it in. Do I need a Libary to accomplish this? There is a great deal of confusing information to me available, so study suggestions would be wonderful. Eventually I hope to set this up via a RS-485 network.

If you can send the data to serial monitor you are mostly there. Switch the out put to a serial port that the XOJO app can listen to. It is beyond the scope of the Arduino forum to know how to make XOJO read the data.

What kind of data can XOJO read.

The serial input basics tutorial may be of interest.