Use the AWS access and secret keys for your user that has permission to call:
codebuild:StartBuild
codebuild:BatchGetBuilds
codebuild:BatchGetProjects
logs:GetLogEvents
s3:GetObject
If using Jenkins as source provider your user must also have permission to call:
s3:GetBucket
s3:PutObject
If the access key or secret key are not specified, the plugin will attempt to load credentials from the DefaultAWSCredentialsProviderChain.