After following the instructions for installation of the PyMol plugin, you should see a login screen. Use your 3DM credentials to log in.
If this is successful, the plugin will inform you with a dialog:
You may now use the menu in the top left of the plugin window to use the plugin. Navigate to 3DM Menu > Structures > Load structure from 3DM.
Select the "Nuclear Receptors - Ligand Bidning Domain (Demo 2008) (NR-demo-2008)" system from the dropdown. A list of PDBs will load. Select 1A28A. Click "Load structures"
The 1A28A structure will load in the main PyMol window. This may not happen instantly, as the structure must be retrieved.
If you see this structure, congratulations! You can start working with PyMol and 3DM. If you encounter any errors during this process, please refer to the Troubleshooting guides for your version of PyMol. (1.8, 2.3)