Wordpress Woocommerce Expert Needed -- 2

What is needed:

A user goes to checkout and selects "custom shipping method 1" or "custom shipping method 2" in the Shipping Methods area.
There are 5 shipping methods, I only need this for 2 shipping methods:

If "custom shipping method 1" is selected, user clicks Next, an item is added to the cart with name "custom shipping method 1" with price 0, continue checkout
If "custom shipping method 2" is selected, user clicks Next, an item is added to the cart with name "custom shipping method 2" with price 0, continue checkout

Else ---> Any other shipping method is selected (not the 2 above) ---> don't add any items, continue checkout

I am using an AJAX checkout plugin (WooCommerce MultiStep Checkout Wizard)
Their website - https://codecanyon.net/item/woocommerce-multistep-checkout-wizard/8125187.

I cannot provide site access or FTP access.
You need to do it on your local machine.

Any reply without " I have fully read and understood what needs to be done and I can do it without site access" will be ignored.