code: Exactly what to add, where to add, and what to remove

I'm really nervous about this step. I have the .htaccess open and I have the code visible that needs to go in to .htaccess. I don't know exactly where it's supposed to go. The instructions say " add the following to your 'htzccess file in / / / / replacing other WordPress rules." I don't know which lines of code are the WordPress rules. Does this new code go at the end between # BEGIN WordPress and #ENE WordPress?