This is a basic documentation as to how to install the TRD 747-400
To install this Add-On, one MUST have a Minimum FG V.2020.3, but the FG V.2020.4 is recommended
Download Link for the zip file.
Extract the file like you would've done with any other Addon Aircraft.
Move the unpacked directory to your custom addon aircraft directory you've specified.
Rename the extracted directory/folder to 747-400. Make sure that the 747-400 directory does not contain another subdirectory/sub-folder (this can happen with WinRAR). If so, move the inner 747-400 directory/folder outside.
To update, delete the 747-400 directory and install the latest version.