You should water a peperomia plant once the top 1-2 inches of the soil dry completely and then water the plant thoroughly.
Watering peperomia plants is the point when things most commonly go wrong. Overwatering is the number one problem that people have when keeping peperomia plants indoors. Many of us have a tendency to kill out houseplants with kindness by being a little too enthusiastic with the watering can.
Peperomia plants will do best in bright, indirect sunlight. An east or west facing window sill is ideal for them at most times of the year. The only thing to watch for is to ensure they don’t get excessive direct sunlight during the summer months, as this can cause leaf scorching.