SKULabs automatically attempts to link known shipping methods to the requested method but we're very conservative to not mistakenly link a requested method like Express AM to Express.
Where SKULabs does not automatically choose a method we have a few ways to set the shipping method on orders:
Shipping method links are links between your store's shipping methods like "Ultra Saver Shipping" being mapped to "Least Expensive" or "FedEx® Ground (2-3 Days)" to "FedEx - Ground".
You can permanently hide or show specific rates like Media Mail and Library Mail on the enabled methods page.
If you want to use rules to select a specific method using more criteria than an exact match of the requested method, shipping rules can be configured to set a default for a wide variety of criteria such as specific SKUs, order value, or number of items.
Finally, on your store settings pages you can set a default shipping method per-store which is the least important of the settings and will be overrode by any others settings.