This is how you enter the discount code successfully:
On a computer: when you have accepted the terms and entered your contact information in the next step, a summary of the ordered products will open on the right side of the page. Below the products is the section: "Discount code or gift card code". Enter the discount code in that box and click "Apply" next to it. Now the discount should be reflected in the price.
On mobile: after you have accepted the terms and moved to the contact information section, at the top of the page immediately under the text Saaren Taika Shop you will see the section "Show order summary", click to open it and enter the code "Sale code or gift card code" - to the tray. After that, click the arrow button on the right side of the tray. Now the discount should be reflected in the price.