Phoca Gallery Slideshow Plugin is a content plugin. It means, such plugin can be inserted into the article and its output can be designed using CSS and HTML in editor. An example might be the plugin alignment in article, such as centering.
The following code will center the plugin in the article:
<div style="background: yellow; width: 500px; text-align: center;">
<div style="margin: 0px auto; width: 300px;">
Yellow color was added to the code to display the effect of centering, see output.