Just like advanced and all other nutes....... micro first, stir the rinse the spoon off then grow, stir and rinse and finally bloom, stir and rinse then you can add your micros. Its important to rinse off the spoon so the nutes aren't being combined in raw form, you'll actually see salt flakes in the mix.
You'll need all 3 parts during all growing phases so don't add more of one mix just because you're in flower, follow the directions.
You should be using reverse osmosis water with an air stone going at all times to keep your mix moving
I do a water changes every 10 days during veg and every 7 days in flower, its overkill but I feel better knowing my plants will always have the nutes they need