Helen,
You can currently access enterprise server services that are federated with your Portal.
ArcGIS for AutoCAD will prompt you for your credentials to access the portal.
ArcGIS for AutoCAD 370 currently does not understand your identity within the Portal so you will only see items (services) that have been shared with everyone in the organization.
The next release of ArcGIS for AutoCAD 400 will have a full concept of identity so you will be able to directly access your content and layers shared with you and your groups. This next release will also add support for hosted services both in Portal and Online. Currently ArcGIS for AutoCAD 370 does not support Hosted Services.
-Don