The only time to adjust this is during character creation at the beginning of the game or is there a way to do it later also?

Once you leave the general area of Goodsprings, you can alter your character for the last time.

You can change them, when you leave Goodsprings.

There are also perks to increase them, some outfits affect them, and later on you'll find a medical way to modify them (if you pay attention).

Thanks!