If you downloaded the FormRouter or pdfscripting tool, the downloaded code needs to be unzipped and installed in a very specific directory determined by your computer system, product and version installedd. Both sites should provide some installation instructions. But if you are using any version of Acrobat newer than 10.01 or Windows Vista or newer there have been some major directory changes and the sites should provide some information about those changes.
The above products will add the document level script and form fields needed for the date picker to work within a form.
As noted you need to provide a lot more information for a usable answer to be provided.