Need to manually install package flysystem-aws-s3-v3 not found in filesystemmanager

Question

I tried to install manually flysystem-aws-s3-v3 to write in aws s3 file server. In fact, i can't access to the console because i only have ftp access. I used php download website but in filesystemManager.php in Illuminate\Filesystem the class is not found. I tried to change composer.lock and composer.json and add all dependencies contained in php donwload zip. I modified the autoload files and i can't understand what is lacking. The problem it can't found the class :

Class 'League\Flysystem\AwsS3v3\AwsS3Adapter' not found in FilesystemManager.php line 197

I thought it'd be possible to manually install the package. If someone knows what is missing