Go to the WooCommerce menu, Settings submenu, Shipping tab.

The list of your shipping zones is displayed. Click on the Modify link at the end of the line for the shipping zone for which you want to set up a Shipping Zen method.

If you have not yet added a Shipping Zen method for this zone, see first: how to add a Shipping Zen shipping method

💡If you’ve already set up a Shipping Zen shipping method for one shipping zone, you can reuse it for another zone using our export and import functionality [Pro version only].

In the table of available shipping methods for the shipping zone, click on the modify link [2] at the end of the line for the method you want to set up:

In the shipping method settings screen, scroll down to field 4 Calculation of shipping rate and enter the weight of the packaging in field [3] in the image below:

The weight of the packaging you have just entered will be added to the weight of the products in the cart to calculate the shipping rate by weight.
See here how to set up a weight-based table of rates.

If the weight of your packaging varies greatly depending on the products you are sending, we recommend that you group your products into shipping classes or product categories, and then set up several shipping methods. You can choose to display or hide each method depending on the product classes or categories contained in the cart.
See here how to show or hide a method depending on the cart contents.