can i make a theme?

can i make a theme or template in dreamweaver and publish it and use it and work the content from wordpress admin?…beacause i downloaded the connections theme and i uploaded the site into dreamweaver and i put the downloaded folder of the connections theme and put the site and in the wordpress admin it was theron the presentations>themes and when i selected it it didnt show alf of the theme and the image was missing from the header all i saw was the outline…..can someone tell me what i can do with that or can i just make my won theme in dreamweaver using css?
Thank You