You can add the following concurrency primitives to your Concurrency Model:

You attach an event or operation message to a link with a concurrency primitive, but to attach an operation message the primitive must first be associated with a class.

Use the appropriate icon on the Concurrency Diagram toolbar to add a concurrency primitive to the diagram, or you can drag a concurrency primitive from the dictionary.

When you have added a concurrency primitive, you can change it through the concurrency primitive's Property pages, including linking it to a class.