I’ve never made scented sand, but maybe it is similar to making scented salts. For that, I simply mixed the salts in a bowl, then added soap color and fragrance. Put a tight lid on the bowl and shake until the color and fragrance are well mixed. With the salts, the vigorous shaking prevents clumps from the liquid scent and color–I imagine sand would be the same way. If you are really concerned about that, I’d recommend using a dehydrator on low (put wax paper down first, obviously).
I’m curious as to what you want to do with the sand. Is it supposed to be like potporri, put it in a bowl and let the fragrance disperse? If so, you might need a fixative for the scent–check out perfume making for different types.
Good luck with your venture