Just drag an empty circle on the element border from the element to another one. If there is only one possible relationship type for the particular case it will be inserted. Otherwise, a context menu shows from which you can choose a type of relationship you want to insert.
Insert Relationships Using Smart Connector
Tutorials| 17 September 2018 14:36:27 Dusan Rodina - softwareideas.net
Smart connector makes adding relationships between diagram elements quick and easy.