Replacing full size circuit breakers with tandem breakers is a viable way to get the space you need. The 2-pole circuit breaker must connect to both bus bars.
Are there any additional instructions that I need to follow while doing this?
Workmanship standards. Don't cut wires too short. All wires should have a service loop. i.e. the connected thermostat, light switches, outlets, should be able to be pulled out six inches. Use deep boxes where ever the wall depth permits.
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