After your first few hundred or so Sims have moved in you'll be prompted to plop your City Hall - This is quite a large building and has numerous expansions that make it even bigger, so allocate it to a decent sized plot as in the image below.
So, now you have everything basically set up, hit the fast forward button to cheetah speed sit back and watch your residents move in and hopefully your City's income too. Soon you'll need to start adding some more RCI, so head on to the next page for some more advice.