@suzie.ravier you can review this post How to encourage bees to fill the Flow Frames to see lots of info on the topic, but I also encourage you follow the Flow Hive facebook page and watch their videos-- they are super helpful and I don’t know which one, but there is one that has information on applying wax to the frames. https://www.facebook.com/pg/flowhive/videos/?ref=page_internal
In short form however, I had a block of bees wax (not a candle, not anything that would harm the bees) that I slid back and forth across the front of the frames like you would drag hard cheese on a cheese grader. A quick 3 or 4 passes on each side and that was that. I had some excess comb in one of the frames from the brood chamber that the girls had built in the wrong spot that I also grabbed and just pressed into the edges of the super frames to encourage the smell of their own hive to apply to the super. Thats the magic in my opinion.