Add the round and pick the Coding Test card
Add a round and pick Coding Test on Basic Details. This is the sandboxed, auto-scored assessment. If you want a voice interview that happens to include code, pick AI Interview and set the round type to Coding instead. That one runs 20 + 10 min with a code editor in the room.
Coding Test is its own Interview type card. The Coding round type is the voice version.