Are you wanting to set the attributes from something external to the HE hub, or within the hub?
If external, then I would suggest installing the Maker API built-in app, adding your device to the list of devices in that app and calling the "Send Device Command URL" from your external app / service, passing in a parameter for the value, e.g. the setTemperature command. See here for more details.
If internal, i.e. you want to set the temperature of a device from within the HE hub, then you can use Rule Machine to call a custom command of setTemperature, passing in the temperature value. I can offer some more details if this is what you are after.
