Hi Ian,

You can edit it in the clients.php filed located in the Sections folder.

Or go to Appearance > Editor. Expand the sections folder and select clients.php.

However, most of the HTML is located within the Clients Widget.

So if you wan to customize the CSS for the clients section use the Custom CSS field in the Custom Code section in Parallel Options Panel.

Use the following CSS selector,

.clients img {width:100%;}

You can change the percentage to whatever you want.