Connect to DynamoDB using NoSQL Workbench and the IAM role ARN option

I am trying to connect to DynamoDB using NoSQL Workbench and the last option i.e. IAM role ARN, but I am getting the following error:

Missing credentials in config, if using AWS_CONFIG_FILE, set AWS_SDK_LOAD_CONFIG=1 How to fix this error?

Moreover, The pre-requisites for using an IAM role are not clear. I have the following queries

1. Do we use IAM role ARN in combination with our temporary credentials?
2. Do we use the IAM role option in combination with our IAM credentials?
3. Do we create a role, then the policy, and then assign it to our IAM user?
4. How to get a working IAM role ARN for connecting to DynamoDB using NoSQL workbench?

Thanks