The bracketed photos you selected in Lightroom are aligned and merged into an HDR image displayed in Photomatix Pro.
You can now adjust the image in Photomatix. Try different presets to choose a style you like, and then refine by adjusting the settings.
When satisfied with the result, click Save and Re-import.
As we have chosen the option to re-import on the Plugin's dialog, the image will not display in Photomatix Pro, but will be automatically saved and reimported into Lightroom.