Double-click
Double-click on the text to edit the text. The edit text dialog will appear.
Enter the new text and click the 
button.
Interactive Edit
To edit text interactively first select it.
Selected Text
Drag any rotate manipulator 
to rotate the text.
Drag any scale manipulator
to re-size the text.
Drag the rectangle to move the text.
Text Properties Dialog
You can also edit the parameters of the text using its properties panel as shown below. To view the properties panel first select it.Then right-click on it, then select Properties Panel from the context menu that opens.
Text Properties Dialog
Text
Text to be placed
Font
Font style of the placed text
Height
The height of the text
X
The X coordinate of the center of the text
Y
The Y coordinate of the center of the text
Center
Center location of the text
Alignment
Alignment of the text