you can use merge fields
you can find it in Insert - Merger Fields
On a layout while in layout mode, those merge fields will look like this:
<<YourCityField>>, <<yourStateField>> <<YourZipcodeField>>
It's also possible to use a calculation field that combines the values of the three fields, but if your only need is to display the values on a layout as you have specified, the calculation field method is not needed.
My standard practice where I have name fields (first middle last) and address fields (city state zip) I create FirstLast and LastFirst, I concatenate these. I always have a field CSZ (trim(city)&", "&trim(state)&" "&trim(zip). This way the fields are ready any time I need them.