Basically, they will just put a drop in each eye to expand the pupils and take a photo of the back of your eyes to check everything's fine. That's what'll happen if it's the same one I have haha
You'll be left with blurry vision for a few hours so don't drive yourself to the appointment as it would be dangerous to drive yourself back home again. Also, take your sunglasses with you as everything will appear bright as a result of the eyedrops.
Taking the photos will allow them to see if there is any retinopathy at the back of the eye. The place I get it done sends me a letter to tell me the results.