Connectors define specific relationships between specific elements, so you usually create them directly on the diagram by dragging the required relationship type from the Enterprise Architect UML Toolbox. As for elements, the Toolbox automatically presents the connector or relationship types appropriate to the type of diagram.
Create two elements on the diagram. Click on a connector in the Toolbox, click on the source element in the relationship, then drag across to the target element. This creates the selected connection between the two elements. If you double-click on the connector, the connector Properties dialog displays, and you can define the characteristics of the relationship.
Note: Enterprise Architect has a very useful feature. To find out more about the type of connector you have dragged on to a diagram, right-click on the connector and select the UML Help menu option. This displays a Help page on the connector type.