You just need to select the specific product you are interested in. When you go to the product page, you can add it directly to the cart in your desired size, or you can click on it to view a more detailed description or additional photos of the product, based on which you can then order the item in your preferred size.
Please select the size you would like to order from the options on the right side of the product image. For each size, the estimated delivery date to the carrier is shown. If this date works for you, just click the "ADD TO CART" button.
In the top right corner, you will see the shopping cart icon. When you hover your cursor over this icon, a window with the cart contents will appear. If you click on it, the page with the complete contents of your shopping cart will open, where you can confirm your product selection by clicking the "CONTINUE WITH YOUR ORDER" button. After that, you will need to fill in your details and specify your delivery and payment preferences.