crashed twentyten trying to add hader image to theme fucntions

Don’t edit the Twenty Ten theme. Instead create a child theme for your changes. Once your child theme is active, we should be able to help with the customisation. For now, try switching to the Twenty Eleven theme by renaming your current theme’s folder in wp-content/themes and adding “-old” to the end of the folder name using FTP or whatever file management application your host provides. That should get you back into your site again. The delete the Twenty Ten theme and upload a fresh copy.

ok, took copy of themes function php from new download on my local computer and copy pasted to server file themefunctions.php. now error

Fatal error: Call to undefined function add_action() in /hermes/bosweb25c/b1502/ipw.siobhan/public_html/wp-content/themes/twentyten/functions.php on line 51

line 51 reads:

/** Tell WordPress to run twentyten_setup() when the 'after_setup_theme' hook is run. */
add_action( 'after_setup_theme', 'twentyten_setup' );

if ( ! function_exists( 'twentyten_setup' ) ):

not sure where to go form here. this should be an uncorrupted file form fresh download. but I cannot get to admin anymore to work from inside.
any help appreciated

ok got back in, reloaded theme functions in proper file. Now

A couple of questions :
when I add an image for custom header–where is it stored?
If I am using catagory templates two: it should let me crete differeint headers for catagories…but where do I enter that data? whre would I find instructions

thanks for your help

when I add an image for custom header–where is it stored?

In your Media Library.

If I am using catagory templates two

Sorry? Category templates two?

I know I sound really stupid but what is the folder name for my media library. In admin folder their is an image folder. In content-themes there is an image folder but I cannot find “media Library’ folder or whatever in my site directory so what would it be called. I can use the admin panel to upload a custom header image, see it on the site’s page but cannot find the physical file inside the site.

the other is I am trying to use a plug-gin called Categories two. it is supposed to enable me to have different headers for categories pages which is what I am trying to do in the first place… not crash my site.

All of your uploads are usually stored in wp-content/uploads. They may also be split into separate month/year folders (check Settings -> Media). With regard to the plugin, I can only suggest that you try posting on that plugin’s dedicated forum via it’s Extend page.