A/C is not blowing as cold as it used too? on 2002 Honda Civic

My car takes R134a and i was wondering will buying that from Autozone, etc do the trick?

Asked by for the 2002 Honda Civic
If the ac is working properly then you just need a top up but I would have it leak tested first
And what did you mean by top up. I dont know much about car A/C systems. Is this something i can do myself?