To add a symbol, left-click on the symbol in the diagram palette, and then left-click on the document. The currently selected tool will revert to the pointer tool, so to add another object, click on the symbol again, then on the document.
To draw a line between two objects, right-drag between the two objects, starting at the attachment point area you wish to start the line with, and ending at another appropriate attachment point area. The initial ordering of the lines may not be correct (lines may overlap, for example) so to reorder lines on a particular side of a object, select a line, then left-drag the desired end to a new position (tip: keep within the object perimeter). Left-dragging the line end can also be used to change the attachment point of that end of the line, to a new side or vertex (depending on the object).
To select or deselect a object, left click the object. To select several objects at once, keep the shift key pressed down when left-clicking, or left-drag a 'lassoo' around several objects.
To delete a object or line, select it and press the Delete key, or use "Edit|Clear", or right-click on the object to show a menu and choose the "Cut" item.
If you are deleting a object which has one ore more lines attached, the lines are deleted prior to the object deletion.
Shapes can be rotated by right-clicking and selecting "Rotate clockwise" or "Rotate anticlockwise".
Line arrows can be added (pointing in the direction in which you created the line) by selecting the line and pressing the "Toggle arrow" tool on the formatting toolbar.