Regardless of the file type you used to create your network, you can easily update it anytime.
The process is almost the same as when you create a new network, but, in both cases, you need to be inside the network you want to update (not the workspace view).
- EPANET (.inp) file
You can replace the existing EPANET file with a new one by dragging & dropping it into the interface. - GIS files
You can replace the existing layers with new ones by dragging & dropping them into the interface. Alternatively, click on the Layers button and then Add data. In both cases, name your files exactly the same as the original ones.
You can also add new layers to the existing ones. In this case, the files should have different names.