Here is a mini tutorial.
1. Open your image in Photoshop
2. Open a new document - 800x600 pixels should do the trick.
3. Drag and drop your image that you opened onto the new document.
4. Then adjust it to the size, e.g
5. Duplicate this layer and name it reflection.
6. Go to Edit>Transform>Flip Vertical
7. Move the layer so it fits nicely under the first
8. Now click 'Add Layer Mask' and then pick the Gradient Tool (G)
9. Now on the canvas draw a line from the middle, down or up, depending on what your Foreground and Background colours are.
Enjoy 