Put on boots, gloves and safety goggles with a respirator before handling the muriatic acid. Mix one part acid into four parts water in a plastic sprinkling can. Wet the concrete surface once again and soak any surrounding grass or shrubs. Then sprinkle the acid solution onto the concrete. It should bubble on contact. Allow the acid solution to etch for 20 to 30 minutes to neutralize the concrete's alkalinity, and then remove the acid with a broom and plenty of water.
Let the concrete dry for a least 48 hours, and sweep off any residual concrete powder. Now you can begin applying a concrete stain with a roller or brush in any style or pattern you desire. If a second coat is needed, wait 24 hours between coats.