add field in custom module magento admin

go to   app\code\local\package\module\block\adminhtml\module\edit\tab

open file form.php  add custom field


                                                $fieldset->addField("lastname", "text", array(
"label" => Mage::helper("storeowner")->__("Last Name"),
"name" => "lastname",
));


$fieldset->addField("email", "text", array(
"label" => Mage::helper("storeowner")->__("email"),
"name" => "email",
));


in prepareForm function
here are  2 field has been added in this example