As it’s Christmas we’re using a start for this tutorial but a sparkling highlight can be added to any object with this technique, although you'll find it will look more natural if you choose a subject that has a reflective surface that would normally have shiny highlights.
Step 1: Open your image
Open your image and select the Brush Tool. To get a star shape click on the little to the top right of the brushes palette where the arrow is, right of the menu and load the Assorted set. You’ll be asked if you want to replace the current brushes click OK.
Step 2: Change your brush
Go back into the menu and pick the preset star shape you want to use. We chose the one numbered 50 and we’re going to make the brush size quite large for this tutorial. Around 200 pixels is fine for our image but how large your brush size should be will depend on the object and the size of the image you’re working on.
Step 3: Pick a colour
When you have your brush selected, click on the Colour Picker found at the bottom of the Tool Box and select a suitable tone. An off-white that has a touch of yellow in it works well if you want a warm sparkle.
Step 4: Add your starburst
Move your cursor around the image clicking on the areas where you want the 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.
Step 5: Add a touch of blur
If you want to adjust the strength of the starbust simply reduce the Opacity slider or go to Filter>Blur>Gaussian Blur and add adjust the slider to add a slight amount of blur.