We have two entities that we want to create a relationship for.

It's simple – just use one of the tools from the toolbar:

• One to many (press 6)
• Many to many (press 7)
• Association (press 8)
• Inheritance (press 9)

If you've already selected the tool, simply drag from one entity to another.

Aaaand... you're done! If you want more, you may click on the relationship, and in the right panel, you'll be able to update this relationship, and change the color of it.