After download, unzip to a folder of your choice.
All folders and files needed are in this folder.
Start sailingPD.exe from this folder.
In case you only want just new software, not all data files, do the full download and move the resulting executable to your own SailingPD folder where you keep your SPeeD data files.
Make sure you do not overwrite the data files you edited so carefully to suit your situation!
HTML example files are included in the download but also available on the separate page HTML files. There they will be updated when new html (from users) arrives. This new html will only be included in the full download when there is an update of SailingPD itself.