How to tame a carno:

1. Get a carbonemys, preferably one with a lot of health if the carno is high level

2. Get some tranq arrows and a crossbow, then equip the crossbow in your hotbar

3. Mount the carbo then find a carno

4. Equip the crossbow while you are on the carbo then start shooting at the carno

5. Just keep shooting at it with your crossbow while your carbo tanks the damage until the carno starts running away which if you are lucky your carbo will be left at half health

6. Dismount from your carbo and start chasing after the carno while still shooting it until it falls unconscious

7. Feed it meat until it tames while watching its torpor.