In Taskheat, the link arrow points to the task that depends on the task the link originates from.
If task "A enables task B," it also can be read as "B depends from A." In other words, "A→B" means that task B depends on task A and can be marked as completed only if task A is marked as completed.
To link two tasks, you need to use the outlet on the far right of the task view. Drag the "worm" from the enabling task to the dependent one.