Put on tight-fitting undergarments and a t-shirt before you put on your sauna suit. This will help you to feel more comfortable inside of the sauna suit and also keep the material of the suit from chaffing against your skin.
Put on your sauna suit, making sure to tighten any applicable bands around your ankles or wrists for optimal insulation. Remember that any opening will let in cool air, releasing your body heat, and allowing your sweat to evaporate. This will defeat the purpose of the sauna suit.
Drink plenty of cold water while you're in the sauna suit (at least one 8 oz. glass for every 15 minutes you're in the suit). While wearing a sauna suit you will lose sweat at a prodigious rate and will need to replace that lost moisture by drinking water.
Relax in your sauna suit for up to 30 minutes, enjoying the relaxing warmth and the feeling of sweating out any impurities from your system.
Remove the sauna suit, when done, while standing in your shower or bathtub. This will prevent any accumulated sweat that pours out of the suit as you take it off from making a mess in your home.