Bathing or showering is not restricted by an ostomy. You should bathe or shower with the entire appliance on, or the entire appliance off on your appliance change days. The water or soap will not hurt or damage your stoma although make sure to thoroughly rinse the soap off your skin if bathing without the appliance, so that the new appliance can attach properly. Do not let a shower stream fall directly on your stoma. If bathing with your appliance on, just dry the pouch with a towel, or use the cool setting on a hair dryer to dry.
Hot tubs are also okay, but note that long soaks in a hot tub, or in a warm bath, may lessen the normal wear-time of the appliance and you may need to change it more frequently.