Hi Helen and Tim -
I'm Greg, an installation specialist and 9 year Windows MVP here to help you.
If you have a Microsoft account then you sign in with that password, unless you specifically set up a Local Account which has its password changed in Settings > Accounts > Sign in options.
See How to change the password of your local account in Windows 10 here: https://www.digitalcitizen.life/how-change-your...
But it's unusual to have a Microsoft account and not use it to Sign In to WIndows 10. For one thing, you'd have to sign in to all the individual apps and games that are tied to your MS account, and it has a bad habit of then converting your Local Account into the Microsoft account - something we help with a lot here.
So try the password change at that location to see if it's available. If not then look at Accounts > Your Info to see if an email account is listed at top. If so then you definitely use a MS Account to sign in on that PC.
I hope this helps. Feel free to ask back any questions and keep me posted. If you'll wait to rate whether my post helped you, I will keep working with you until it's resolved.
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