Changing masthead image in Portal 7.3

Hi,

I want to change the masthead image after copying one SAP standard theme.

Now from Content Admin->Portal Display->Related Links->Download Theme Type I want to download the theme. But for each theme I get three entries:portal,ur,its respectively. I am not sure which one to download. Please clarify.

Besides after updating the theme, how can I upload it again on to the portal?

Regards

Arindam