The temperature setpoints aren’t exposed in the UWG Grasshopper components, so you would have to use Python to achieve this. It can be done in many ways, I think the easiest way is to clone the github repo for ladybug/uwg, open up the DOE Reference Buildings in Excel, modify the temperature setpoints in your buildings as desired. Then open up a terminal, navigate to the main uwg directory, and type
python -m uwg.readDOE --serialize. This will cache your changes in a readDOE.pkl. You can run the UWG from python directly, or if you want to do it in Grasshopper, swap this pkl with the one Grasshopper is currently referencing (in your Rhino folder). Then all your new simulations will reflect the changes you have made to the reference buildings.
I can go in more detail if needed.