Open Steam and sign in
Go to the Battlefield 6 store page in your Library or Steam Store
Make sure you have purchased or preordered the game
Wait for the preload option to become available before launch
Click the preload or pre-install button if it appears
If the game is already in your Library, open its page and start the preload from there
Keep Steam open and let the download complete
Check that you have enough free storage space
Make sure automatic updates are enabled in Steam
If preload is not available yet, check again later before release
Launch the game after the official unlock time once preload is finished