Add XML/MyYahoo/Etc. buttons to theme

Hello ~ I just installed WP 1.5.1.2 this evening, I also installed a theme. Everything is running fine but I can’t figure out how to customize more. I would like to add xml/add to my yahoo buttons, have the code to do so, but where do I put it? This is my first time using WordPress so thank you for all of your help! ??