Select the Sauté setting and heat the olive oil in the Instant Pot. Add the celery and onion and sauté until the onion begins to turn translucent, about 5 minutes.
While the celery and onion are cooking, heat the water in an electric kettle, in the microwave (in a microwave-safe measuring cup), or in a small saucepan on the stove. When the water is boiling, stir in the Better Than Bouillon to dissolve.
Stir the frozen vegetables, tomatoes, and kidney beans in with the celery and onions in the Instant Pot, then pour in the broth.
Secure the lid on the Instant Pot and set the Pressure Release to Sealing. Cancel the cooking program, then select the Pressure Cook or Manual program and set the cooking time to 5 minutes at high pressure.
When the cooking program ends, perform a quick release by moving the Pressure Release to Venting, or let the pressure release naturally. Ladle the soup into bowls and serve.