Hello! Welcome to Mysidia :D I joined in around May I think it was lol.
Do you mean changing the look of your site? I found it to be really difficult trying to install a theme so I went the only route I knew how which was code it by using CSS in the files. I changed the look of my site just by altering the theme that was already on the site. You can see how my site looks here
www.wildhorsetracks.mysidiahost.com (my site isn't available yet, it's still being worked on and beta testing isn't open yet)