You can create a web form visually in Dreamweaver by inserting form elements into a page, but that's only part of the job. The other, more complex part is developing a mechanism to handle the data your visitors submit with the form. The data is sometimes saved in a customer database, for example. Typically, web application technology such as PHP or Adobe ColdFusion handles the form data.
This article describes how to create a simple web form. Developing a mechanism to handle submitted form data is beyond the scope of the article. For detailed instructions on building forms and a mechanism to handle submitted data with PHP, see this tutorial series on Adobe Developer Center.