There are a few accelerator keys that can help editing the circuit:
Select all objects on the sheet
Deselect all objects
Rotate the selected objects 90 degrees clockwise
Delete the selected objects
Place the currently selected part
Parts and wires can be selected by clicking on them, and by holding the Shift-key while clicking, you can select multiple parts and wires. You can also select objects by 'rubber-banding': hold down the mouse button while dragging the pointer over the objects that you wish to select.