Twin breakers

In the US, tandem breakers are more expensive than 2 single pole breakers Many panels do not accept tandem breakers so you would have to use

one slot chording From bar one the conductor goes to the top of slot one , than to bottom of slot four and then to bar two breakers similar to those

two slot 2) If the panel is maxed out, you may be able to install tandem breakers in a few slots Look at the panel label or remove some bottom breakers

two slot toaster A tandem circuit breaker connects two independent 120V circuits, both necessarily on the same leg since it's a single slot in the load center A dual pole