How to add strings in .po file after adding php code

My webiste language is Chinese, I am able to use Poedit to translate the default woocommerce-zh_TW.po file and it works perfect. But I recently add following code in cart.php in order to add a RETURN TO STORE button in cart page, the code works great, the only problem is the RETURN TO STORE button is still English.

“><?php _e( ‘Return to Store’, ‘woocommerce’ ) ?>

I understand I am not able to translate it because the string doesn’t exist in my woocommerce-zh_TW.po, how can I add the string in my .po file?

Here is my website: http://www.jpincense.com/cart/