[otrs] logo, header and footer changes

Hello, I would like to seek help on how exactly to modify the look/feel of OTRS based on the DTL files. For example, I wanted to modify the customer.pl look, so I modified (the title, for example) CustomerHeader.dtl, CustomerFooter.dtl, CustomerLogin.dtl. But, the changes are not reflected whenever I go to customer.pl. Specifically, I edited this line: <td class="header"> <a href="" class="headeritem">My Company Name here</a> </td> and <td class="footer">My second Footer line here</td> But, nothing :( Can anyone please tell me how to do this? Thanks much. Great job on OTRS