How to use cart api in flow designer

[Anna_Servicenow]

I have used the below script that i found in community to create two ritm under same REQ. I did run it from background script and it is working fine. How can i trigger it from flow designer so that this is triggered as soon as request is submitted. 

var catalogItem = 'b70c34e807334c10540bf2508c1ed073'; // catalog item sys_id

var jsonArray = [{"requested_for":"Abel Tuter","requested_by":"Sam Jone","model":"Hyundai","quantity":1,"device_model_name":"Car-Petrol"},{"requested_for":"Fred Luddy","requested_by":"Amy Jone","model":"Honda","quantity":1,"device_model_name":"Car-Diesel"}];

var cartId = GlideGuid.generate(null);
var cart = new Cart(cartId);

for(var i=0;i<jsonArray.length;i++){

var jsonObj = jsonArray[i];
var parser = JSON.parse(JSON.stringify(jsonObj));

var item = cart.addItem(catalogItem,1);
cart.setVariable(item, 'requested_for', parser.requested_for);
cart.setVariable(item,'requested_by',parser.requested_by);
cart.setVariable(item,'model', parser.model);
cart.setVariable(item,'quantity', parser.quantity);
cart.setVariable(item,'device_model_name', parser.device_model_name);

}

var rc = cart.placeOrder();
gs.info('Request Number is: ' + rc.number);