Before you enter data into your table (see Lesson 10), you should make very sure that you have included all the fields you'll need. Why? Because if you add a field later, you'll have to go back and enter a value in that field for each record that you already entered. In addition, if you change the field length, you risk truncating or invalidating data that's already been entered.
You can add a field in either Table Design or Datasheet view. Let's try it in Table Design view first, since we're already there:
Select the field before which you want the new field to appear.
Click the Insert Rows button on the toolbar, or select Insert, ...