The contact form solution pack is not an extension for Creating Forms. there is nothing to install in Dreamweaver.
A solution pack is a collection of PHP scripts that have been created to perform a certain task.
See the description on the Solutions landing Page:
php-scripts-and-solutions/
What are PHP Scripts and Solutions?PHP scripts are pre-built code snippets that perform a specific task or function. PHP solutions on the other hand are complete pre-built applications (composed of PHP scripts) or pages that add rich functionality and design to your website. Our solutions can be easily customized using any text editor, including Dreamweaver and our Dreamweaver extensions.
the Contact form Solution pack contains a PHP script called Contactus.php is a contact form that has already been crated.
You need to follow the instruction's in the read_me.html file for modifying the WA_Globals.php file to provide information on your site.
See the Getting Started guide on the Contact Form Solution Pack support page in the Getting Started Section for more specifics:
contact-form/
