Before buying, you can find pre-order information on the product page where it is written in green. It will also be stated at checkout. Not all products are pre-order, so if you don’t find this information then the item is already in-stock and will be shipped as normal. Please be sure to check properly first.
After buying, you will receive an estimated dispatch date in your confirmation email - please be sure to check your spam folder! - and a screenshot of the product page showing the same green text.