"Aldosterone is a steroid hormone (mineralocorticoid family) produced by the outer section (zona glomerulosa) of the adrenal cortex in the adrenal gland. It plays a central role in the regulation of blood pressure mainly by acting on the distal tubules and collecting ducts of the nephron, increasing reabsorption of ions and water in the kidney, to cause the conservation of sodium, secretion of potassium, increased water retention, and increased blood pressure."
As the above poster wrote: healthy diet, meditation (yoga as well if tolerated), sun, water, light to moderate exercise if tolerated, REMOVING STRESSORS, and laughing can all help reduce your cortisol levels. For supplementation, Phosphatidylserine comes to mind and may reduce high cortisol. But definitely try to remove your stressors as much as possible, don't feel obligated to please everyone and don't be afraid to say "No" when asked to so something.
The addition of a healthy mineral Sea Salt such as celtic Sea Salt may also be beneficial.