Food: Look at feeding at least once a week, leaf litter will be a key food. Options include and not limited to veggies such as peas, carrots, cucumber, melon, proteins sources such as dehydrated shrimp, sardines, even algae wafers to round out the diet. Calcium is important as well. Provide sources of calcium such as egg shells, oyster shell, or cuttlebone. A reptile calcium powder can also be used. Temperature: Generally room temperatures work for most isopods. Look for specifics on the specific species you purchase.
Environment: Isopods are prone to climb out of some setups, so make sure your habitat has its top seal to avoid escapees. You may use a glass enclosure or even a Sterlite style shoe box or plastic tubs/totes. Key is to set up an enclosure that can maintain humidity and temperature. Airflow is key as well. Make sure to cut holes in plastic tubs in accordance to the requirements of your particular isopod species in question. Some isopods such as dwarf whites like a mostly enclosed high humidity setups. Others need airflow, holes on each side of the tub, etc.
A standard setup includes a corner of the setup with sphagnum moss kept moist. This may include water crystals to prevent drying out. Mist roughly half your setup weekly to provide ambient moisture. Most of the remaining setup can have a base layer of ABG substrate, and a thick layer of leaf litter on top. Include a piece of bark as well for shelter. Avoid coco fiber which can compact.