Smurfing, or less derisively "making an alt account", is a way to player under an account other than your main player account.

On Nintendo Switch

1. Purchase the Nintendo Switch Online Family Plan, this allows your online account to be linked to multiple Switch Profiles.
2. Create a new Switch user profile
3. Launch Killer Queen Black under this secondary user profile

On Steam

1. Sign out of Steam
2. Sign up for a new account. You CAN use the same email address associated with your existing Steam account
3. You will be sent an activation email. Make sure to click 'create my account' not 'find my account'
4. Complete sign up process and sign in as new user.
5. You should see Killer Queen Black in your library with a button that says borrow under it.
6. You're now smurfin!