When in a timeslot view, you can drag the task rectangle up and down. Doing so will automatically reschedule the task to another time, adjusting task's start and end time accordingly. You can also pull upper or lower side of the rectangle, resizing it. Doing so will automatically adjust task's start time (if you pull upper side) or end time (lower side) and adjust task's duration accordingly.

Also, double-click a task in any view will open this task's detail screen.