Changing size and margins on logo

I need to move my logo up and to the left in my pda template, and also have it display 100% of the width of the screen. I can't figure out where to do this. I tried making my logo larger, but it appears to have been scaled down automatically.

I've tried to upload an attachment here, but the "Add File" button isn't working.

Can you tell me where I can put CSS that will apply to the header image in the pda template?

I still can't upload an attachment - tried in FF and Chrome.