WordPress.org

Where can I insert WP Glideshow?

You can Insert WP Glideshow almost everywhere you want (Pages, posts, template file)

Where can I edit the Stylesheet?

You don't have to edit the Stylesheet you can make changes directly in your Administration Panel (Settings --> WP Glideshow)

What is perfect Resolution for the Images?

You can choose your own resolution on plugin-settings page. Remember to regenerate thumbnails after changing image sizes.