The IONIQ 5 is equipped with an Electronic Parking Brake (EPB), which you can find these set of buttons on the panel on the right of the steering wheel as shown in the picture below.
To release the electronic parking brake, press the button and it will be released. Then, turn the gear knob clockwise to D (Drive) on the extreme top, and off you go!
To reverse, turn the gear knob to R (Reverse) on the extreme bottom.
To turn off the vehicle, press the button that states P (Park). The small parking brake button (it's the "P" sign with a circle around it) will be lit up. You'll see the same sign on the button lit up on the dashboard.