I would just set the lights to that, and to the schedule you want, tonight and see how it goes.
If you want to go more slowly I would increase hours of max light each day, lets say by an hour, until you reach your 1:8:1, then I would increase your light intensity each day, lets say by 10%, until you reach your goal.
This is not a very intense light, and your tanks is fairly deep (for this light anyway), I think the risk of shocking the corals with too much light, especially the hardy corals you have, is pretty low.