It sounds as though you have a working WRF domain, so it should be relatively straight-forward to build a WRF-Hydro configuration using your domain files (geo_em.d0*.nc). The first question is whether you have access to Esri ArcGIS (ArcMap, ArcGIS Pro, etc). If you do, then you can use the WRF-Hydro ArcGIS Pre-rprocessor,
here. On the releases page, you can find documentation and test domains. If you do not have access to an Esri license, there is a Beta open-source GIS Pre-processor,
here. There is less documentation, and the open-source version will require you to build a suitable python environment. Please consult the
documentation and
presentations to learn more about how the tools work. You will need to bring your own DEM and get familiar with the tool settings and how they will impact the hydrologic components of your grid. We suggest you start by building simple model configurations first, and ensure the model is working well before coupling to WRF.