If the "check engine" light is on it would be a good idea to check what codes are present. If you have an AC code that will lead you in the right direction.
Even if there are no AC related codes the vehicle may disable the AC for unrelated codes. This is done to encourage the owner to repair a system some people would otherwise ignore. This is becoming more prevalent in newer vehicles.
If the AC works but just blows slightly cool air then it's likely low on refrigerant. The system will need to be leak checked and topped up. There may be a trouble code stored without the check engine light illuminated since the AC system is technically non-essential.
AC repairs are a real challenge for a novice so you will likely need to take it in for repairs.