- In the Toolbox, select the Gradient Tool.
- On the Options bar, choose gradient sample and style.
- Click on the image to define starting point, drag and release on ending point.
- In the Options bar, you can define also blending mode and opacity.
- Dither option (selected by default) creates smoother gradients.
Tip. Just in case you didn't know, the Gradient tool is also available in Photoshop Elements that is way cheaper version.
And if you believe, Photoshop Elements lacks some other important feature, be sure to visit this page.