Child Theme for TwentyTwelve

I am helping a friend build a website using TwentyTwelve. She gave me all the login information for the WordPress website. I added a header image, but the image is below the navigation. My understanding is that I need to add a child theme to move navigation below the header. This is my first child theme but the instructions are clear. The problem is that I only see a wp-content folder in a backup folder for another WP website I built using the X theme. Oddly enough, other themes are also in this backup folder. This is the structure..\BL Backup\wpcontent\themes. In the themes folder are the following folders.
twentyfourteen
twentythirteen
twentytwelve
x
wtchild

Wtchild is the child folder I created to use for twenty twelve. It has a style.css file, but wtchild is not showing up as a theme in my friend’s dashboard. How do I get wtchild to show up as a theme in my friend’s dashboard?

Any help is appreciated and I apologize for the lengthy explanation.