Apply SPF in the morning everyday. Always start with nighttime application of retinol.  If your skin tolerates it and you want to see more visible improvement, you may be able to go up to twice daily. Even if you only use retinol in the evening, be sure to apply sunscreen in the morning. Never apply retinol to skin that is pink/red, dry or irritated. Sometimes this means avoiding the bone around the eye as this skin can become sensitive earlier on than most other parts of the face.