WORDPRESS

I am using wordpress as my website, and I want to change it to a simple shop. I downloaded Woocommerce. But the theme I am using (gridlocked) does not work with Woocommerce, so I wanted to change the page.php (according to the tutorial). But I cannot find the phase.php. And I am afraid that installing STOREFRONT will mess up my existing website. What is the best solution ? Thanks in advance, Rita