error @ http://localhost/drupal when install drupal

First, I am new at Drupal. I am trying to add a submenu item to My homepage/Content/Options above all Add Post, Add Post by type, Add User Post... I would like to add to that submenu item Create new post. When user would click on that item, some kind of create node would show up in the content area.

I have managed so far to add a new link $output .= '<li>'. l('Create new Post', 'mysite/'. arg(1) .'/'. $link .'/'. $page .'/'. 'create') . '</li>'; in Mysite.module, inside the function theme_mysite_submenu. My problem is, that I do not know how to populate the content now. Where should go the code for create new post, where do I link it to Create new Post link? So far I have only worked with path that had a callback function, and then the function would take care of the content. But in the MySite module I do not understand which function is called when the user click on the '<li>'. l($item['label'], 'mysite/'. arg(1) .'/'. $link .'/'. $page .'/'. $key);


I would really appreciate any hint, I am kind of stuck here.


Urska