CMS Made Simple Forums

I just installed CMS and am having trouble applying a template and css to the site. Do I have to createa template myself or can I apply one so it has some color and design to it. I downloaded a theme and applied that hoping it would work but obviously it didnt. I just need help getting the design going, im not worried about content I know I can do that. (Im used to that cubecart crap)

Thanks for any help its really appreciated