How to enable Pay for Order Page / EndPoint in Woocommerce

Hi, i am working on a custom woocommerce payment gateway and i am using Modal / PopUp (when pay order button is clicked) to fill out ur credit card information. So i am going to do the checkout process similar to what Stripe checkout does, meaning it adds an extra step for checkout, cause the normal product checkout process in Woo, is the, 1. Cart Page->Proceed to Checkout. 2. CheckoutPage. 3. (Extra step to allow for Modal payment gateway) Pay for Order Page, which basically has a small summary for your order and personal info (filled out before on checkoutpage) and the final pay for order button, here is a pic of how that page looks, like https://imgur.com/a/fVgY3UJ. 4. Thank You Page (Order Receipt).

So i see woocommerce has an endpoint URL to allow that page to be activated (not 100% sure) which is Pay page – /order-pay/{ORDER_ID} as explained here, https://docs.woocommerce.com/document/woocommerce-endpoints-2-1/

So does anyone know how to activate that Woo endpoint URL for the extra step for checkout.
Any suggestions, cause havent found that many information on that online, cause not may stores enable that extra step, as extra setps are not always good for ecommerce payments but for modal / popup payment gateways its needed, checked the stripe code, but is not quite clear how to implement it.

Any help is gladly appreciated.
Thanx a lot.