By visiting the Nintendo Eshop of your Nintendo Switch, you can now access the pre-order and preload of the Pokémon Sword and Shield games.
This will obviously not allow you to play the games in advance, but simply to download the data so that the installation will be very fast on November 15th at midnight.
Be careful, however, this is a pre-order of the game on the Eshop, in a dematerialized version. You cannot preload if you want to buy the game in physical version.
Screenshots from Serebii.net
For your information, the game weighs 9.5 GB.
As a reminder, a bonus of 12 Rapid Balls will be offered for the first to buy the game, until 15/01/2020.