I downloaded a free WP theme and want to use my own image at the top. Is there a simple way (maybe using a plugin) to swap out the old image with my own?
It isn't really that hard doing it the normal way. If you don't want to touch the code then just create a new image the same size as your old one and name it the same thing (with the same file format). Then just overwrite it in your theme's folder.
What if I want to make the header bigger? What code needs to be altered to do this? Can someone walk me through this?
Go to the directory where your theme is and there is probably a file called header.php and another file called style.css. If you know css and html it should be pretty easy to figure out. Most probably your theme has the header image in style.css so thats all you'll have to edit.
I did the replacing thing, but the default box still stays on top of my custom image. What can I do about that?
What default box? If you want to get rid of it just look in style.css and header.php and it should be in one of those, then you can just delete it.
The default header image box that is blue (if you don't change the color). I think I tried he deleting one time and it messed it all up. But I'll give it another try to make sure.