Select A Task
It's simple, just click on the border.
You'll know you have it selected when the little squares appear at each corner.
Delete A Task
Select the task.
Hit the Delete Key.
Resize A Task
Select the task
Click and drag one of the squares that appear at the task corners.
Move A Task
Select the task.
Click and drag on the task frame.
Remove A Dependency
Click on the dependency line.
Modify Task Properties
Double click in the text area of any task and the task info editor will be presented.