While you can use already cooked lentils or canned kidney beans, if you will be cooking this with dry lentils and beans, it is vital to soak them. If you are using an Instant Pot, this step is less important. Soaking overnight soaking is ideal, but if you're trying to make this for a quick lunch, allow them to soak for at least 30 minutes in hot water to get that perfect texture and taste.