on features - module position it´s written "This theme comes with different module styles, badges and icons. For each module you can pick a style and combine it with an icon or badge to create your own unique look. Here is a list of the available options:"

My question is, how can I apply these different styles to modules?

In Your demo page for example TOP A - modules are shown in a box,
TOP B modules don´t have a box.

How can I reach this?

I´m quite new with Joomla especially to use third party templates. The document on how to use Your template could be quite mor detailed, it didn´t help me much.