So, the first thing you want to do is to use a light source that creates those highlights in the eyes.
Catch lights are the highlights in the model’s eyes. Without them, the eyes look lifeless. So, the first thing you want to do is to use a light source that creates those highlights in the eyes. This means you need a light that is either in front of or slightly to the side of your model. You want the light to create a glint either in the middle or the upper corner of the iris. Your model does not have to look directly at the light source to create these highlights.