[otrs] Developing In OTRS

Hello, I am new to OTRS and I am trying to learn how to create additions. What I want to do is start by adding a new button under the drop down ticket menu. I am unsure where to do this. In a template or by adding to the database. I need documentation on developing. Please see this link to get a better Idea what I am trying to do http://forums.otrs.org/viewtopic.php?f=64&t=10129