1. Open a new document (white background), and create some text.
2. Setup the foreground color to (#000000) then click the gradient tool, and from the drop down menu which should appear in the top left, select the style which goes from black to transparent, like the example below:
3. Click the layers tab, then hold 'ctrl' and click the text layer > now create a new layer.
4. Make sure you've got the new layer selected and the gradient tool, and using the outlined text-shape, drag the gradient tool from the top of the outlined shape to the bottom, delete the previous text layer.. and your end result should look similar to: