I guess you are running SimpleViewer 2 Pro since you just downloaded it.
Which version of svManager are you running? The version number is on the Admin screen. For SimpleViewer 2, you'll need svManager 1.6 or later. If you need to upgrade then please see the upgrade instructions in the svManager manual.
If you have not already done so then please take a look at the instructions for using svManager with a Pro Viewer in the svManager user manual.
The workflow for creating and customizing a gallery with svManager and SimpleViewer 2 goes something like this:
1. Create a new SimpleViewer 2 gallery in svManager
2. Add a few images
3. Download the gallery to your desktop and customize it with the svBuilder application that comes with SimpleViewer 2 Pro
4. Upload the gallery.xml file back to the gallery on your server. Overwrite the old file.
5. Once you have a gallery design that you are happy with then you can 'clone' this design in the svManager galleries screen.
SimpleViewer Support Team.