Wolfenstein: Youngblood has been billed as a cooperative experience, but that doesn’t mean that you have to play it that way. If you would rather play through the campaign by yourself you can do that too.
To start a solo game in Wolfenstein Youngblood you’ll want to select the “Host Game” option and then you’ll need to change the “Who Can Join” options in this menu. You have different choices you can make here, including friends only, public room, or private rooms. The one you’ll want to choose if you want to make sure that noone can join you is the “Nobody (Offline)” option.
Change your join options to this and you won’t have anyone dropping into your game. Click Start Game and then you can play through the Wolfenstein: Youngblood campaign solo. Just because you select the Solo option in Wolfenstein: Youngblood you will still be playing the game with an A.I. companion.
You may want to try and find a friend to play with you for the Wolfenstein: Youngblood campaign though. Playing solo will stick you with the A.I. companion and even the worst of human players aren’t as bad as the A.I. in this game. If you want to open your game to other players you can try using the Buddy Pass if you’ve purchased the deluxe edition or you can invite friends to your game (assuming they own it).