If you want to add a tab to the product edit page, you can do this by following these steps:

1. Create a new tab block  {module_name}/adminhtml_{block_name} class Magestore_{module_name}_Block_Adminhtml__{block_name} extends Mage_Core_Block_Template
implements Mage_Adminhtml_Block_Widget_Tab_Interface
{
public function __construct()
{
parent::__construct();
}
public function getTabLabel(){
return Mage::helper('core')->__('My tab');
}
public function getTabTitle(){
return Mage::helper('core')->__('My tab');
}
public function canShowTab(){
return true;
}
public function isHidden(){
return false;
}
}