Hi and welcome to the forum
First of all, the styles must be installed in Producer. You cannot view styles just in Windows, like you view images.
In Producer, you need to have at least one slide in your timeline (even empty), and selected.
Then, go to Slide Options > Slide Styles and browse through the styles.
Click on each style, and you will be able to see an animated preview, with place holders instead of pictures.
The other option is to browse through the Manage Effects menu, but that will only show you a static preview.