Enclosure
With incredible variations in species and preferred natural climates, this will serve as a general guide that will get you started with pretty much all types, though you may research your particular species to see if they prefer tropical, or more arid environments.
Isopods don't need a whole lot of space, a 6 quart plastic container with a secure lid works great if you have fifteen or fewer isopods, but when they breed, upgrade them to a larger container, whatever size container you put them in, they will breed to fill it up.
Isopods don't require light, they actually prefer darkness, and will be just fine with ambient light from the room they're placed in, though you're welcome to add LEDs so you can view them, give them some darkness during the night.
Your little friends will need air, so make some air vents on the sides of the container, you can also add vents to the lid, though only having vents on top will not be sufficient as they will suffocate, even if you're not stacking the containers, because carbon dioxide will sink to the bottom, and without air flow it will stay there. Having too much ventilation is far better than not having enough. You can use a mesh screen such as what is put on windows to keep them in, and flies or other pests out.
Isopods need moisture, but also may want a place to dry out, most keepers will create what's called a moisture gradient in the container, where on one side of the enclosure there is a large chunk or sheet of moss settled into the dirt, where water is poured on occasion and will be misted with water, then the other side will be left dry, so that the center will be a happy medium.
Substrate
Not only will they live in this, they'll eat it too, so like millipedes or snails, avoid using coco coir or synthetic substrates.
You'll need dirt, so some organic, pesticide and fertilizer free topsoil or compost is great. Mix in shredded wood and leaf litter and you're good to go. Other helpful fillers you can use are sphagnum moss, calcium carbonate powder, worm castings or powdered eggshells. Then sprinkle more leaf litter all over the top, this will be their largest source of food.
Isopods like to dig around, so having several inches for them to explore is good, if the substrate becomes compacted and tough to move, you can gently mix it around with your hands without fear of hurting them, they'll move.
Another alternative substrate is flake soil, which is fermented wood flakes or sawdust, this is seen as an advanced substrate but has been shown to increase longevity and breeding in many types of isopods, as long as other nutrients are added.