Because these animals are from Minnesota lakes, they prefer cooler water. An unheated tank is perfect. The cooler the better, but water up to 72 to 75 degrees should be fine. They will need a substrate three or four inches deep to bury themselves in. Either gravel or sand will work fine.
Mussels have a top and a bottom.
When you collect them it is best if you try to notice which end is up. If you can't remember just lay the animal on its side on the substrate and let it work its own way into the gravel. If you put the mussel in upside down it will smother if it can't work its way out of the gravel. Mussels are filter feeders and will keep your water sparkling clean. The upper one is surrounded by a fringe and is called the incurrent siphon.