Hello all.
I am working on a wp theme. first time really, rather than to start from absolute nothing (that'd be the next try)...
Grabbed a very simple super minimalist template (thanks to zenhabits.org). And for example, wanted to add a sidebar to it.
so in the index.php I added.
the get_sidebar(); function
I do have a sidebar.php in the correct directory.

but get this error msg.
"Fatal error: Call to undefined function responsive_widgets() in C:\xampp\htdocs\wordpress\wp-content\themes\zh2\sidebar.php on line 5"

where do I add/specify functions? is the wp-includes>functions.php the best place?