You’ll need to purchase a ball needle if your pump doesn’t already have one. [1] X Research source
The hole where you insert the needle is a small black rubber circle with a smaller hole. Check with the manufacturer if you cannot find the hole for your ball. [2] X Research source
Another way to check is to hold the ball at chest-level and drop it. If the ball bounces at least to your waist, then it has the correct amount of air. [3] X Expert Source Ryan TremblayBasketball Coach Expert Interview. 13 November 2020.
Hold the handle down until the ball becomes inflated to your desire. Repeat the process and add more air if needed.
Loosen the CO2 valve to release the compressed CO2 into the basketball. Test the ball and add more air if needed.
You could also bring your ball and quarters to a tire pump at a gas station. The only other tool you’ll need is a needle that fits into ball.
Never leave a ball outside and avoid direct sunlight for too long of a period.