You can use the AWS console at https://console.aws.amazon.com/s3/home (make sure you are logged in), which has improved considerably over time, or use a client application like CyberDuck or CloudBerry S3 Explorer.
It is possible to use the free version of CloudBerry Explorer, but it has a couple of limitations:
- There is no CloudFront Manager
- You cannot generate test URLs
- You can only have one S3 Account (with as many buckets as you like).
- No bucket policies.
You could try the free version first and if you want more functionality, you can always upgrade.