To allow containers within a task to interact with S3, we need to create an IAM Role for the task. In the search bar:
IAM
Next, in the left-hand menu:

On the creation page, enter and select the following information:

Next, to grant write permissions to S3:
AmazonS3FullAccess to find the policy.
Fill out the information on the final step:
ECSTaskFullAccessToS3Role (or any name you prefer)Allows ECS tasks to call AWS services on your behalf. (add a description for easy management)
Click Create role to finish.

Done!
