Specific Question about changing header

I have the Green Cordobo wordpress theme. The header right now is what I want to change. I dont know the exact size now, but Its height is small. Now if I want to change it to a customize header and the width will be the same but height will be much bigger, can i do that?

I tried and its just not working.

you can change about anything inside a wp template

If the theme comes with a css file look in there and see if there is a setting for a header graphic. You will have to change the height setting to what you want it to be. It might also be set in a table. You just need to look around and find out what is setting the graphic height.

It can usually be easily done.