If you're used to using the "Run" box to open apps, you can use that to launch Command Prompt with admin privileges. Press Windows+R to open the Run box. Type cmd into the box and then press ...

You can change the admin user on a Windows 10 PC through the Control Panel. However, you'll need to be already logged into an admin account to do it.

If you need to troubleshoot Windows 10, improve system performance, or just want to clear up some disk space, clear your cache.