Yeah zoom in, or move yourself to get the shot you want in the viewfinder.
Pressing the shutter halfway to let the autofocus do it's job is fine. In normal conditions the AF should do a great job. In low light you may need to manually focus.
The settings your using means the camera is sorting all the settings for you - allowing you to point and shoot.
The settings on the top dial give you the adjustability to either allow the camera to sort everything for you in the basic zone, with the presets such as sports, macro, night time etc.
To control things yourself such as shutter speed, aperture, you need to use creative zone settings, P,Tv,Av,M etc.