I think you misunderstood. You can’t load the Water Wave Files at all via blueprints. The Water Wave files are not of type Material Parameter Collection.
These are the Gerstner Wave Files that define the type of Waves for Oceans and Lakes.
I also have not found a way to change the Gerstner Waves directly via blueprints. There is a GetWaves and SetWaves from the WaterBody. The SetWaves is looking for a WaterWaves asset but you can’t load or create one via blueprints.
In a round about way via blueprints you can read the gertnerwave data and set it but you can’t get the Wave for say a lake to actually update. There is a C++ function to RecalculateWave that causes the wave to update but nothing exposed via blueprints.