Set Up a Checkout URL for Meta Commerce Platform

Hi,
I am connecting my website to facebook and instagrame shop, need to set up a checkout URL, there is a step need the website developer help.
Your developer should make changes to your website code to build your checkout URL. Review sample code to see how to build a URL to parse product IDs and coupon codes, then adapt your URL to meet your specific needs.
I don’t understand how to achieve it, possibly could you help to guide me step by step ? or to set it by logining into my website wp-admin.

Step one. the article is as below.
https://developers.facebook.com/docs/commerce-platform/setup-checkout-url

Step two. Build the checkout URL with Code Snippet —-– how to made it ??? I really don’t understand it. could you kindly help me for that? or provide me some useful guide for that?

Best regards
Cathy

following is the example JAVA/SPRING CODE
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import java.util.*;
@RestController
public class CheckoutController {
@GetMapping(“/checkout”)
public Map<String, Object> checkout(
@RequestParam String products,
@RequestParam(required = false) String coupon) {
// Parse products
Map<String, Integer> productQuantities = new HashMap<>();
for (String productEntry : products.split(“,”)) {
String[] parts = productEntry.split(“:”);
productQuantities.put(
parts[0], // Product ID
Integer.parseInt(parts[1]) // Quantity
);
}
// Build result
Map<String, Object> result = new HashMap<>();
result.put(“products”, productQuantities);
result.put(“coupon”, coupon != null ? coupon : “No coupon applied”);

return result;
}
}