AWS - NoCredentialsError Unable to locate credentials

Question

I'm new to AWS and also a beginner in python.

I have a situation in here, I'm facing this kind of issue:
"The NoCredentialsError is an error encountered when using the Boto3 library to interface with Amazon Web Services (AWS). Specifically, this error is encountered when your AWS credentials are missing, invalid, or cannot be located by your Python script. "

 File "/usr/lib/python2.7/site-packages/botocore/auth.py", line 373, in add_auth
    raise NoCredentialsError()
NoCredentialsError: Unable to locate credentials

And I did some troubleshooting by checking the path given, and the credentials are in there.
**[root@xxxxxx aws]# ls
config credentials

Which part am I missing, and where else do I need to check?
Please advice.