Hi James,
You can only set up a PIN if you've set up a password on your Windows 10 user account. Once you set up a PIN, you will have the option to either change or remove it. To remove your PIN, follow these steps:
- Click the Windows logo (Start button).
- Click the gear icon (Settings).
- Select Accounts.
- On the left pane, choose Sign-in options.
- Under PIN, press Remove.
- Click Remove again.
- Enter the user account password, and then click OK.
After doing the steps above, you can sign-out to your account to see if you will be able to log-in using the password.
Let us know how it goes.