Even with the free version you can get results without the watermark.
Just use the steps identified in the popup window when opening the program.
From the HDR menu choose generate. When that's done, from the same menu, choose tone mapping. Only if you save the generated HDR and then open it again for tone mapping will you get the watermark.
Not quite the perfect subject for HDR. Kind of lacks in composition and we don't get to figure out exactly what this is (I think it's a decorative sculpture).
Keep trying though, and just watch what this program does on a dramatic cloudy sky!
This will ultimatley be DQ'ed for the text added by the use of what I assume is a trial program. I like the composition and your take on it though. Need to save at max size for challenges whatever that is for the challenge.