Two ways to access your S3 buckets: jets3t and s3cmd. Jet3set provides UI and s3cmd is only UI.
Here is how to get a file using s3cmd:
First configure the account:
s3cmd --configure
Then, you can use s3cmd to access your buckets. eg: downloading a folder from s3:
s3cmd get --recursive s3://bucket_name/object_name to_local_file