This theme does not have an integrated login system in place because there are many login plugins available and it really depends on who you want to login and for what. But looking at your website, it shows you are using Ultimate Member which appears to have a login form (as I saw on your login page)…. although I just see the shortcode for it in the page and not the form.
Basically any kind of login plugin you use, this will create a login form and possibly a page for members/customers.
If the login form is not working for Ultimate Member, I would recommend contacting their support.
UPDATE: I realized you are using WooCommerce, which has a login form on your checkout page. You may want to find out from WooCommerce if they have a login link or shortcode that you can add to your main menu.
