Once you have added some elements on your canvas, e.g. screens, shapes or images, you can connect them by using connectors. When you hover your mouse over the edge of the element or screen layer, you see magnets that you can click to pick up and start drawing a connector. You can drop the connector on another element. That will be its target. In presentation, connectors become interactive. Once the connector is drawn, you can double-click on it to edit its label. The label can be styled independently from the connector line.