There is a very easy way to upload files to AWS S3, however you can easily get lost with different gems and options available. My favorite way is using paperclip with aws-sdk. Here are some quick steps to get you started, look at the gems homepages for more information.
Then run bundler
Example of what your model might look like:
Note: has_attached_file does not seem to work with create_table
This is how to put it in your form
You also need a create action in your controller. Assuming you used a scaffold, it should work just fine. Enjoy!