Your PACS should provide the option to export DICOM data of a case. It is sometimes on the right-click context menu or somewhere else on the User Interface of your workstation.
The Export function may give you the option to export anonymized data.
If it isn't, ask your PACS administrator.
Otherwise, the usual method is to export the data to a USB drive attached to your workstation, and to import it into Horos from there.
Howard
_____