Tire installation is the job of taking your old tires off the wheels, fitting the new ones, balancing each wheel so it spins smoothly, and bolting everything back on correctly.
It sounds simple, and the mounting itself is quick. What matters is everything around it: checking the wheel for damage before a new tire goes on it, balancing to remove vibration, setting the pressure your vehicle actually calls for, and torquing the lug nuts to the figure in the manufacturer's manual rather than leaning on an impact gun.
Those details are the difference between a set that wears evenly for years and one that gives you a shake at highway speed within a month.