Amazon S3 - Creating an IAM user
In order for Easy Digital Downloads to connect to your Amazon S3 account, you will need to create an IAM user and attach a permissions policy to the user.
First, log into your Amazon S3 account and navigate to the Users page. This page can be found by clicking on your account name in the top left corner and clicking on Security Credentials:
If you get a popup- choose "Get started with IAM users"
If you have an existing IAM user you wish to use, click on that user. If you need to create a new user, click the blue Add User button and follow the prompts.
You now need to obtain security credentials and also attach a permissions policy to the user.
Click on the Security Credentials tab and click Create Access Key.
Once the success message pops up, click Download Credentials. Save the file to a secure location on your computer.
Note: you will not be able to access the secret key ever again for this user, so make sure that you save the file. If you lose the credentials, you will need to create a new access key.
You can click Show User Security Credentials to view the access key and secret key. These are the values you need to enter in your WordPress site at Downloads → Settings → Extensions.
Once a user is created and you have obtained the access keys, click on the Permissions tab and then click Add permissions:
Then choose "Attach existing policies directly":
In the Filter box, enter "S3". That will filter the results down to those that are relevant for Amazon S3.
Check the box for AmazonS3FullAccess and click Attach Policy.
Your IAM user should now have full permission to access and upload files to the S3 bucket.
If you need more assistance creating IAM users or attaching policies, see Amazon's guide on creating IAM users for more information.