With the desired brush selected. Click on the colour picker and choose a suitable tone. I went of an off white that had a small amount of yellow so it has a warm sparkle. Move around the photo clicking on areas where you want a burst to appear. Do not drag as this would paint a succession of stars. Choose areas with natural highlights and don't go over the top. Edges always seem to look good with a burst. You can change the brush size if you like to vary the effect. At this stage you could leave the photo and consider the job done, but, in the words of Chris Tarrent, "we don't want to do that".
Let's look at how these starburst can be made to glow like a rainbow.