You can change or modify text after entering it.

To insert new text, simply place the text cursor at the location where you want to insert the text (click once with the left mouse button).  Text you enter from your computer keyboard will now be inserted in the location you have chosen.

 Most other text modification operations will require that you first select the text to be modified. To select a single word, double-click on it. The word will be selected (it will be highlighted in dark blue).