Media S3 is different from other media_[PROVIDER] modules in that it requires MUCH more configuration before the file gets to the Amazon S3 bucket. Instead of relying on YouTube, Vimeo, or Archive.org to create the video in the correct codec and a thumbnail, Media S3 expects that you have already done this. This can be done with a commercial encoder, FFMPEG, or a cloudbase service like Zencoder. However the files are transcodered and transferred is S3, Media S3 is checking an S3 bucket for video files and automatically adding them as Media entities.
Nothing in AmazonS3 needs to be configured. To configure AWS SDK you either need to enable the awssdk_ui module or add these settings to your settings.php file.
$conf['aws_key'] = '...';
$conf['aws_secret'] = '...';
$conf['aws_account_id'] = '...';
$conf['aws_canonical_id'] = '...';
If your server's CURL library is out of date, you well get an error like...
There was a problem using S3: exception 'cURL_Exception' with message 'cURL resource: Resource id #303; cURL error: SSL read: error:00000000:lib(0):func(0):reason(0), errno 104 (cURL error code 52). See http://curl.haxx.se/libcurl/c/libcurl-errors.html for an explanation of error codes.
If you have permission to make updates to the server, update curl and php5-curl. With most linux flavors, it's as easy as...
sudo apt-get install curl php5-curl