Well, there are a number of ways. You can download a Photoshop brush and use that. I have found that some brushes work fairly well although if you’re working with a high resolution image, forget about it. You could also create the flare on your own using soft, round brushes and a little bit of ingenuity. Abduzeedo has a lot of great lighting effect tutorials on his site. You can use a combination of his effects to create a similar effect. This however takes time to do. So how can you create cool, nice-looking lens flare effects quickly?
A couple months back I came across a program called Knoll Light Factory. It comes packed with options and effects for creating lens flare effects. Check out this tutorial from YouTube.
The software costs $149 to buy and $89 to upgrade. You can download the demo and try it out for yourself!