you only need to have an empty database, and a connection to the empty database. Power CMS Builder will create the tables that are needed in the database that you specify.
In your Dreamweaver site, are you using a local testing server or a remote testing server?
if you are using a local testing server, connect to the local mysql server using PHPMyAdmin, if you are using a remote testing sever, connect to the remote MySQL server in php my admin, then create a new blank database.
in dreamweaver, you will need to create a connection to the database.
you may want to review the "Defining a Dynamic Site in Dreamweaver", "Creating your database connection in Dreamweaver", and "Managing your live database settings" tutorials on the learning resources page.
once the database connection is created, you can create a new CMS content area on your page by selecting the part of the page that should be converted to a content are and going to WebAssist -> CMS -> Add Content to Power CMS
after the area is converted a power cms content area, you will be prompted to upload files to the server and begin the Power CMS installation. this will create the Power CMS tables in the database and create the power CMS Admin pages.
you can then log into the power CMS admin area to manage the content of the content areas.