You can move a task into another list in two different ways:
1. Select a task by clicking on it, a move icon should appear at the far left side of the task. Drag your task to the desired list in the sidebar on the left side of the app and release it if your mouse is exactly over it.
2. Select a task by clicking on it and click on the edit icon on the far right side of the task. You can then change the list of your task in the edit task overlay by selecting a different list via the list dropdown.