Step 2: Options for merging and saving
If your photos were taken hand-held, check the Align Images option and select the by matching features alignment method. If your photos were taken on a tripod, use the by correcting shifts method.
If there were moving people or objects in the photos, check the Remove ghosts option. Otherwise, do not check this option, as removing ghosts reduces the quality of the merged image.
Check the Use Half Floating Point format option to save disk space. The Half Floating Point format is appropriate for storing very large variations in brightness, as it is used by OpenEXR, the most popular 32-bit HDR image file format.
Check the Scale pixel values to fixed range option to set an initial exposure to display the merged image so that it doesn't show bright for a bright scene and dark for a dark one.
Finally, click on the Merge button to process the photos and create a 32-bit HDR image file that will be loaded into your Catalog as shown in step 3.