Sequencing LED around a retinol routine
The straightforward approach is to keep them on the same evening but in the right order: cleanse, LED session on clean dry skin, then apply your retinol afterwards. LED needs bare skin to work on, and applying actives beforehand serves no purpose.
If your skin is in the early weeks of building retinol tolerance, alternate instead. Use retinol on two or three evenings, and on the off nights run a session in the Calming mode (blue and green light) to help skin look less reactive between applications. Many people find this makes the build-up phase considerably more comfortable.