I hope I am understanding your question correctly. The answer to my comment did help! If it is a node form that you're trying to add to the menu, this is typically done with a hook_menu() function in Drupal. Here is some sample code to get you started
function YOURMODULE_menu() {
// Here, substitute in the URL of your page. It can be mymodule/add_content or whatever else you'd like
$items['YOUR_PAGE_URL'] = array(
'type' => MENU_CALLBACK,
'title' => t('YOUR PAGE TITLE'),
'page callback' => 'drupal_get_form',
'page arguments' => array('your_node_function'), // Here, you should put in the function that creates your node form
'access arguments' => array('Administer content'), // This is optional, you can require a user to have certain permissions set to access your page/form
);
return($items);
}
Remember to clear your cache before you test it!
Sample code in your function that is creating the form:
function your_node_function($form, &$form_state)
{
$form['field_1'] = array(
'#type' => 'textfield',
'#title' => t('Field label'),
'#description' => t('Help user understand what to input here'),
'#required' => TRUE,
);
return $form;
}
See if you can see this tiny one-field form to get you started. This doesn't explain how to actually save the user data, etc because that is outside the scope of what a single answer here can provide, but this should help you get started on a form that's hooked up to the menu system....
I hope this helped!!!!
=================== EDIT ===================
Here is online documentation for the different types of form elements you can add to forms in Drupal: http://api.drupal.org/api/drupal/developer!topics!forms_api_reference.html/7