How does the shipping element work?

We have successfully installed the plugin and extension but cannot understand the shipping side of things?

We selected the preselected Epackets but we cannot see any calculation being made? Does this need to be setup separately?

The system does not seem to import weight and dimensions into WooCommerce so I m finding hard to grasp how shipping can be calculated?

If we change the carrier to aliexpress we still see no changes. Also if a carrier is changed do the product need to be reimported?

Thanks in advance