Open Papyrus and go to Help-->Check for Updates and bring the installation up to date and restart if required.

If not already installed the plugin Requires a version of "Papyrus for UML Developer Resources" greater or equal to 5.0.0

The Plugin is provided via the model-ua update site : https://model-ua.auto.tuwien.ac.at/updates/releases

Open Papyrus and go to Help-->Install New Software, click on Add and enter the link.

Alternatively the releases can be downloaded here as archives : https://github.com/model-UA/papyrus-opcua-plugin/releases

Open Papyrus and go to Help-->Install New Software, click on Add and then on Local or Archive depending if you extracted the archive or not.

If the last step was successful you should be able to find the following packages:

OPC UA NodeSet SDK provides the underlying functions required for reading and writing to NodeSet files.

OPC UA Profile provides a UML Profile which eases creation of OPC UA Information Models.

OPC UA Companion Specifications provides UML models of the NodeSets provided by the companion specifications.

OPC UA Modelling provides a new Diagram Type for Papyrus according to the graphical notation of the OPC UA Foundation.

To get the OPC UA Modelling option inside Papyrus install the following packages: - OPC UA NodeSet SDK - OPC UA Profile - OPC UA Companion Specifications - OPC UA Modelling

When the installation is done restart Papyrus.