Hi jelevens. Welcome to the forums.
such that he can update the menu, news, events, etc.
Pretty much any CMS allows for that, so you might have to do some research and decide which one looks best to you. I suggest you look at ones like ExpressionEngine, MODx, SilverStripe, ConcreteCMS, Drupal etc.
how I would go about implementing it
That's too big a question. First decide on a CMS to use, then look at the docs for that CMS, which will describe installation and usage.