The question is a little TOO simple, unfortunately. Without having more information, all I can really provide you with is some general information.
The Modbus Simulator gets installed with the LabVIEW DSC Module. That's an extra addon to LabVIEW that brings various things, such as Modbus communication, into LabVIEW.
For what you're doing, it's likely you'll be able to work with the Modbus library you linked. It's a free library, although not supported by NI support. If you have formed questions, you can typically post those here and get some guidance.
What you're going to need to do first is take a step back and look at your product. You want to change a value on the temperature controller. Where does that value exist on the controller? Modbus has registers that you can use as whatever variable you'd like. You'd need to look at the controller's documentation to see where they look for the temperature setpoint. Without that documentation, the simple question becomes a brute forced nightmare. Once you have that, you can take a look at the examples that come with the Modbus library you linked to find a way to modify the specific registers you're interested in.
