Expand the Local Users and Groups from the left side of the window, and select Users.
Right-click somewhere on the blank space found in the middle section of the window, and click or tap on New User. This opens the New User window, where you can enter all the details about the new user account.
Type the user name and, optionally, its full name and description.
Type the password to be used for that user and confirm it.
Select the User cannot change password check box.
Click Create and Windows immediately creates the user account. When you are done creating user accounts, click Close in the New User window.
Press the Win + R keys to open Run, type secpol.msc into Run, and click/tap on OK to open Local Security Policy.
Expand open Local Policies in the left pane of Local Security Policy, click/tap on User Rights Assignment, and double click/tap on the Back up files and directories policy in the right pane.
Click/tap on the Add User or Group button.
Click/tap on the Object Types button.
Check all the boxes for Object types, and click/tap on the OK.
Click/tap on the Advanced button.
Click/tap on the Find Now button, select the name of the user or group
Click/tap on OK.
Click/tap on OK.
When finished, you can close Local Users and Groups.
Reference:
https://www.digitalcitizen.life/geeks-way-creating-user-accounts-and-groups
https://docs.microsoft.com/en-us/windows/security/threat-protection/security-policy-settings/user-rights-assignment