You need to click on the "New wastage" button. It will take you to a new window from where you can perform the operation.

Choose from which store you want to load the scrapped goods from and at what price to scrap them. Then select the items to scrap, their quantity, unit price excluding VAT, discount on the item itself, or on the entire operation. If your company is  VAT registered, it will automatically be added to the amount .

To finalize the operation, click on the "Save" button, in your list of wastages, you will find all the wastatges so far.