To add a fixed fee to a product with Magical Product Fees, follow these steps:
In your Shopify admin, go to Online Store > Apps and open Magical Product Fees.
Click Create fee.
Choose the Function Method (recommended for most stores).
Enter a title for your fee.
(Optional) Add a description in the Details field to explain the fee to customers at checkout.
Under Type, select Product.
In the Calculation section, choose Fixed amount and enter the fee you want to charge.
Set how often the fee applies:
Every product: The fee is charged for each item.
Once per product: The fee is charged once per product, no matter the quantity.
For bundling, select Matching Product if you want the fee linked directly to the product or Other Product Fees if you want the fees bundled together and be able to exclude them from discounts.
Choose which products the fee applies to:
All products
Specific collections
Specific products
Custom conditions (set your own rules)
Click Save.
Your fixed fee will now be added to the selected products in your store.