I prefer to sign in to Windows with PIN instead of using password. If you want to do the same then start System Settings (press Windows + I). Click Accounts and then Sign-in options. Now at the right panel click Add below PIN
Verify your account by entering your password and click OK
Enter your PIN and then again to confirm it. If you want your PIN to have letters and symbols, then select Include letter and symbols. Click OK
Now you can see two different buttons
You can change your PIN with Change and you can remove it with Remove.