The Documents folder can be opened in/with Windows Explorer. It should be up the near the top.

You can also navigate to it:

Open Windows Explorer and select the "C:" Drive > Users > YourUserName > Documents > Flight Simulator X Files, the scroll through until you find the Â-52 Cleared for takeoff (KNKX) file

Replace YourUserName with your Windows login name (i.e. if your login user name is John Smith, then you select the John Smith folder).

See attached image.

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