Configure the Login ID: it’s for the Univocal Login ID associated with your account registered on Authorize.net in the section API Login ID and Transaction Key.
The transaction key is the Univocal key used to authenticate requests to Authorize.net. Access your registered account on Authorize.net and recover this information in the section API Login ID and Transaction Key.
The Md5 Hash is the unique key to validate the answers from Authorize.net like you can see in the screenshot above. It should be set identical both in plugins settings and Authorize dashboard.