Hi Sylvia,
Open the Settings App.
Go to Accounts - Your Info.
On that window, there should either be an option to 'Switch to a Local Account' or the option to 'Stop automatically logging into apps with this account'.
Select whichever of those two options exist, that will switch your Windows account to a Local account.
Wait a few seconds, then you can click the option to add a Microsoft account to your user and add the details of your own Microsoft account to the user.