This bath salt is meant to be dissolved in warm bath water before you get in. A common approach is to sprinkle the salt evenly into the tub while the water is running, so the granules disperse and the foaming component can create a light lather. The exact amount depends on your bathtub size and personal preference — if you use it for the first time, start with a smaller amount and adjust next time. There is no single correct measure for every tub; a small handful or a few tablespoons is a reasonable starting point for a regular bathtub, but you will find the amount that feels right for you.
As for the water itself, warm, not hot, water is usually better for a bath product like this: it helps the sea salt dissolve fully and feels gentler on the skin. Fill the tub, add the salt, give the water a swirl with your hand to break up any clumps, and then soak. For an evening wind-down, 15 to 20 minutes is a typical length of time, but you can shorten or extend it depending on what feels comfortable. If you notice any irritation during the soak, get out and rinse your skin with clean water.
After the bath, you do not need to rinse it off immediately — leaving a thin layer of the bath water on the skin can contribute to the softer feel. Pat your skin dry with a towel rather than rubbing hard, and if your skin tends to be dry, follow with your usual body lotion or oil. The jojoba oil in the formula can help reduce the tight, stripped feeling, but it is not a substitute for a moisturizer if you normally need one.
A few practical notes: avoid using this product on damaged or broken skin, and if you have very sensitive skin or a known reaction to essential oils, fragrance or foaming agents, test it on a small patch of skin first or start with a smaller amount. Keep the bath salt well away from the eyes. After the bath, rinse the tub with water to remove any slippery residue from the oil and foam. Store the container closed in a dry place, because salt can absorb moisture from the air and form clumps.