How to change windows 10 user accounts.

The fact that a user account is local is not relevant.  The important factor is whether it is a Standard user account or an Admin user account.  Either of these types can be local accounts or online accounts.  Yours appears to be a gmail account i.e. not a local account but an online one.  I think that the absence of the Family & other people entry from Settings, Accounts indicates that yours is a Standard user account.

You can check or change the account type -

Right-click on the Start button,

Control panel,

View by - Small icons, so you can see everything,

User accounts,

[This dialog shows you whether it is a Standard or an Admin account type],

If it is a Standard user account then click on Change your account type & select Admin - you will need to put in an Admin account's password to authorise this.

Unless there has been a serious fault on your computer, there will be an Admin account on it [the account you created when you installed Windows is always set up as an Admin account during installation].  If that User accounts dialog shows that your account is a Standard user account then there ought to be another account - look in C:\Users for the names of accounts on the computer.  One of them will be your account, you will also see default / Default.Migrated and Public.  There ought to be another unless you have never logged into it.  If not then double-check in the Registry by running RegEdit and looking in

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList

at the entries beginning S-1-5-21- which lists all accounts you have created as long as you have logged into them at some point.

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Use the Built-In Admin in Safe mode to create a new Admin account

If there really are no other accounts on your computer then a Built-In account called "Administrator"ought to appear if you restart in Safe mode.  It has no password.  You can use it to create a new Admin account [see below].  It is important to log off that Built-In account as soon as you have created the new account and made it an Admin account as faults on the Built-In account cannot be fixed and you would have to reinstall Windows.  If no Built-In Admin account appears on the login screen in Safe mode then I think your fault is so serious that reinstallation would be your only option because it would indicate that Windows believed that there was still another Admin account on the computer even though you cannot find it. 

While you are in Safe mode & logged into the Built-In Admin, create a new Admin account with a password 12345 [you can change the password later so just keep it simple initially], open a Command prompt and enter these commands [do not call the NewAdmin account "Administrator" as that has special meaning for Windows and avoid spaces in the name just to keep things simple]

net user /add NewAdmin 12345

net localgroup Administrators NewAdmin /add

After you have logged into the new account successfully at least once & have rebooted to test that you can log into it during normal Windows use, hide the special Built-In account by opening an elevated Command prompt and entering this

net user Administrator /active:no

You can change the NewAdmin's password to something sensible now.  Make sure you write its password down somewhere secure.

You can continue to use your existing gmail account for all activities but will have to use the NewAdmin account to authorise such things as installing applications.

Denis