I would add in the plants before adding in the fish, because disturbing the environment while the fish are inside the tank would cause them undue stress, In my experience the best method is to get your substrate in the tank first add in enough water so that there is an inch level above your substrate, add in your plants and aquascape it in whatever configuration you please, then add in a plastic bag use this to diffuse the water as you fill the tank as to reduce the amount of clouding that can happen during this part. allow your tank to cycle for a couple of days constantly checking twice a day during dawn and during sunset for ammonia, nitrate, and ph level as plants can in the beginning cause havoc on your tanks water conditions before becoming stable.