You need to select (or highlight) blocks of text to carry out some commands
 
Action                 With a mouse...             With a keyboard...
Select (highlight)     Move the mouse cursor       Move the cursor to the
text                   to the point where you      point you want to begin
                       want highlighting to        highlighting, using the
                       begin. Then hold down       DIRECTION keys. Then hold
                       the left mouse button       down the SHIFT key while
                       while you drag the mouse    you use the DIRECTION keys
                       across the text. Release    to highlight your text.
                       the mouse button to
                       end the selection.