To create a dependency (link) between tasks hover mouse over the source task and click a linking circle
drag it to the start or end of the target task until it becomes orange, and release the mouse button
The result would be as follows. Please note there was a one cell horizontal space between tasks before linking. Once link is done, Gantt Suite moved second task as close to the end of the first task as possible. This is because Gantt Suite is working in ASAP mode.