CSS stands for Cascading Style Sheet, which are used to define the look and formatting of a page written in HTML.
You can write your own CSS for your ekmPowershop template, or download readily available CSS templates and upload them into the CSS section of the File Manager (which can be found within the Design section of your Powershop account
If you are using a CSS file, you would need to enter the HTML to reference the file within your custom template.
Most ekmPowershop templates however have in-line CSS coding, which means the code for the CSS can be accessed by editing the HTML for your chosen template.
To do this, go to Design > Template then click on 'Edit Icon' located underneath your themes preview image. Select 'Edit in Custom Mode' from the drop down menu and you will be presented with the HTML code for your template and any inline CSS thats included.