In this article we can see how to create an app user.
Separate App User is required for development purposes. We cannot use the SharePoint System Account for App Installations as it will run in high-permission mode.
Open Active Directory Users & Computers to create the new user.
In the appearing application, choose the New User as following.
Enter the user information.
Click the Next button. Enter the password and you may choose to use the Password never expires option.
Click the Finish button in the next page.
Open Control Panel > Users > Give other users access to this computer.
In the next tab choose Administrator option.
In the next page click the Finish button.
Now the user is created & assigned permission to the computer. You can test by logging in as the new user.
In this post we have created an App User.