The PreBlend button is designed to help organize your layers for manual exposure blending. This page also includes demos on some exposure blending workflows.
This first video shows the PreBlend function to automatically stack, align, and sort exposures.
This next video shows how to use the "BlendIf" option in PreBlend. This approach to blending is designed as a quick and simple approach, but its use is mostly limited to situations where one part of the image is substantially brighter than others (such as interior real estate images with windows to a bright exterior). Blending manually through luminosity selections (as shown in other videos below) is almost always capable of better results.
While it is outside the scope of the support material to comprehensive describe how to manually blend exposures, here are some videos which show a few important workflows to blend your exposures manually after using PreBlend.