No, not in your template manager. But on the module editor inside the module manager.
To publish different slides with different content you have to create a "custom HTML" module, add your content (for example a text, image etc.) to it and publish it on the first slider position. Than create a second module, add another content and publish it on the second slider position etc.
Adding content to your Joomla website can´t be done by editing the templates CSS file.
How you could create a "custom HTML" module is described in the templates read me file.
Here is the short version: Click on "extensions->module manager" in your Joomla backend. A list of all available modules will appear. Click on the "new" icon in the upper right corner to create a new module. Select as type "custom HTML". Than the modules setup screen will appear.
On this screen you can add a modules name, select the position AND add your own custom content (and the small "HTML" icon...)