$this->setTemplate(myphtml.phtml);

<?php

namespace NamespaceModulenameBlockAdminhtmlModulenameEditTab;

/**
 * Modulename edit form main tab
 */
class Main extends MagentoBackendBlockWidgetFormGeneric implements MagentoBackendBlockWidgetTabTabInterface
{
    /**
     * @var MagentoStoreModelSystemStore
     */
    protected $_systemStore;

    /**
     * @var NavGametypeModelStatus
     */
    protected $_status;



    /**
     * @param MagentoBackendBlockTemplateContext $context
     * @param MagentoFrameworkRegistry $registry
     * @param MagentoFrameworkDataFormFactory $formFactory
     * @param MagentoStoreModelSystemStore $systemStore
     * @param array $data
     */
    public function __construct(
        MagentoBackendBlockTemplateContext $context,
        MagentoFrameworkRegistry $registry,
        MagentoFrameworkDataFormFactory $formFactory,
        MagentoStoreModelSystemStore $systemStore,
        NavGametypeModelStatus $status,
        array $data = []
    ) {
        $this->_systemStore = $systemStore;
        $this->_status = $status;
        parent::__construct($context, $registry, $formFactory, $data);
    }

    /**
     * Prepare form
     *
     * @return $this
     * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
     */


    protected function _prepareForm()
    {
        /* @var $model NavGametypeModelBlogPosts */
        $model = $this->_coreRegistry->registry('gametype');

        $isElementDisabled = false;

        /** @var MagentoFrameworkDataForm $form */
        $form = $this->_formFactory->create();

       //  $form->setHtmlIdPrefix('page_');

        $fieldset = $form->addFieldset('base_fieldset', ['legend' => __('Game Information')]);

        if ($model->getId()) {
            $fieldset->addField('nav_game_type_id', 'hidden', ['name' => 'nav_game_type_id']);
        }

           /*   $fieldset->addField(
        'title',
        'text',
        [
            'name' => 'title',
            'label' => __('Title'),
            'title' => __('Title'),
            'required' => true,
            'disabled' => $isElementDisabled
        ]
    );*/

         $this->setTemplate('myphtml.phtml');

        if (!$model->getId()) {
            $model->setData('is_active', $isElementDisabled ? '0' : '1');
        }

        $form->setValues($model->getData());

        $this->setForm($form);

        return parent::_prepareForm();
    }

    /**
     * Prepare label for tab
     *
     * @return MagentoFrameworkPhrase
     */
    public function getTabLabel()
    {
        return __('Game Information');
    }


    /**
     * Prepare title for tab
     *
     * @return MagentoFrameworkPhrase
     */
    public function getTabTitle()
    {
        return __('Game Information');
    }

    /**
     * {@inheritdoc}
     */
    public function canShowTab()
    {
        return true;
    }

    /**
     * {@inheritdoc}
     */
    public function isHidden()
    {
        return false;
    }

    /**
     * Check permission for passed action
     *
     * @param string $resourceId
     * @return bool
     */
    protected function _isAllowedAction($resourceId)
    {
        return $this->_authorization->isAllowed($resourceId);
    }

    public function getTargetOptionArray(){
        return array(
                    '_self' => "Self",
                    '_blank' => "New Page",
                    );
    }
}