You just unzip the plugin in your :
\Program Files\Adobe\Photoshop 7.0\Modules externes
or more likely for a US version
\Program Files\Adobe\Photoshop 7.0\plugins
Start Photoshop open a PSD
In the "File" menu in the "Export" you will see a "bright" item just click on it,it will open a save dialog to export the picture.
Beware it can fail perhaps if there is too many layer I don't know for sure .
At least it won't crash your PSD.
I hope it's clear enought

Feel free to ask.