On your team game plan under the coaching tab, you'll have the option to set your team for triangle, flex, motion or fast break. You can set your distribution in the player game plan, also under the coaching tab. Make sure you're playing the offensive set you are practicing under the practice plan. Basically your offense is going to be a set-it-and-forget-it thing.
Defenses are in the same location, just in the right column. Everything above applies as well, although you'll also want to adjust your positioning with your defense on an every-game basis based on the tendencies of your opponents and the strengths of their team.