Coco-fiber is an excellent substrate for terrestial sals. It can be used alone or mixed with soil without any additives (fertilizers, vermiculite, pesticides, etc.). Keep the substrate moist but not wet and have 3-4 inches of substrate for adequate burrowing. I recommend spot cleaning substrate for feces a couple of times per week and completely changing substrate every 2 months. There should also be hides and as someone else said, a shallow water dish to help with humidity - use spring water or declorinated tap water.

Temps should not exceed 74 degrees for any prolonged period of time - can lead to stress. These sals can tolerate low temps (e.g., 50s) but not high temps. Also keep the vivarium out of direct sunlight.