is identified by the heavy border.

You can change the active cell by:

Moving your cursor keys

Moving your mouse cursor and clicking on the new cell

Typing a new cell address in the name box.

The mouse cursor becomes different depending what you are doing and where it is located on the Excel screen. In the worksheet area, it is usually a "plus". When you begin typing in a cell it will change to an I beam which is a short vertical line.

Entering information is as easy as selecting a cell, and typing the data.