Mouse Actions
This is a fairly mouse-intensive program, designed for you to grab and drag items easily.
Task Commands
Click in the middle of a task bar and drag it left or right
Move the Start/End Date of a Task
Click on the right side of a task bar and drag it left or right
Adjusts the End Date of a Task
Click on the left side of a task bar and drag it left or right
Adjusts the Percentage (%) Complete of the Task
CONTROL + click middle of any task
Selects the Task, and allows multi-selectiong.
Double-click on any task
Shows Properties Dialog
Arrow Icons
Click any arrow to reposition a task in the project hierarchy.

Timeline Commands
Click on Timeline bar then use middle scroller
If your mouse has a middle scroll bar, you can swish the timeline back and forth using the middle mouse scroller.
Scroll bar on bottom of Gantt
You can also use the Scroll bar to change the timeline
Click Zoom in / Zoom out icon
Change your timeline view with Zoom in and out