Aqua Man said:

The increased CO2 allows photosynthesis to happen more efficiently... Otherwise the plants start going into photorespiration.

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...but before you start to consider running CO2, so you’ll really learn to grow without it first. You need to get at least a few grows under your belt and get to know the plant and it’s life cycle, and how it reacts to different stresses and other things during its life cycle as well as how the strain grows, as they all grow differently and have varying traits.
Once you have all that, as well as your temp, humidity, watering cycle and amounts, nute schedule and amt’s, lighting distance and strength during each part of the plants lifecycle, and everything else down pat, then and only then should you consider adding co2.
plus, CO2 is ran with a “closed” ventilation system which means there is no intake or exhaust fans or openings to let the CO2 out of the tent (as CO2 is heavier than air and falls to the floor) to let out the CO2, which can kill humans and/or animals in high concentrations).
As such, you usually need to have a large enough tent that you can fit a moveable air conditioner inside and port the exhaust out a nearby window or into another room, or to invest in a mini-split ac unit.