As an example, Rename a file, but this is also valid for a folder.
Select the chosen file. Here's "Austin.Powers.avi".
Press the Menu button on your remote and go to Rename.
Then press the OK button on your remote.
Press OK again. Here the numeric keypad is displayed and everything is selected (in green).
Here you can rename your file using the numeric keypad.
If you want rename using the mouse remote click here