Do I have to do anything to manage my pension?

Nope. You just need to show up for work. Nice, right? You're automatically enrolled in the plan, though in some instances you need to be on the job for a year before you are officially enrolled. Even though you are enrolled and the pension benefits are being credited to you, they aren't 100% yours until you become fully vested; that can take five or more years.

As for the investment decisions: You have none. Your employer hires a firm to invest the pension plan's assets. There is absolutely no work required (or allowed) on your part to manage the pension money.