Nope. Cash-balance plans work just like traditional pensions. You just need to show up for work. You are automatically enrolled in the plan without having to opt in, though in some instances you need to be on the job for a year before you are officially enrolled in the plan. Keep in mind that just because you're enrolled and the pension benefits are being credited to you, they aren't 100% yours until you become fully vested.
The company that your employer hires to run the plan is responsible for all the investment decisions. There is absolutely no work required (or allowed) on your part in the management of the pension money.