Links are used to create hyperlinks to screens. They are the type of event's action that provides navigation through your prototype's screens.
To create a link just drag the widget which should contain the link action and drop it on the desired screen in the Screens panel.
You can also create a link through the contextual menu of any widget on a screen:
Right-click on the widget which should contain the link action and select the 'Add Link' option. A dialog with a drop-down will appear.
Select the target screen from the drop-down labeled 'Internal Screen'.
Press Ok to create the link or press Cancel to close the dialog without creating the action.