Before adding Power CMS to your site, make sure you have the site definition set up properly.
In the Site Definition, set the Remote And the testing server settings to connect to your live server through FTP.
Make sure to use the valid web URL as the URL Prefix in the testing server settings.
In some cases, the FTP conenction will connect bellow the web root, you may need to add the root folder to the Host Directory setting to make sure that the FTP connect is at the site root.
After setting the site settings, create the database connection.
Then add Power CMS to the site.
DW Should upload the files to the server and start the installation.
The DW FTP can sometimes be un reliable, in some cases, you may need to upload the site files using a third part FTP program like File Zilla.