How do you play guitar chords like these?

I'm not sure I understand all your questions, but I think can offer some help. The "x's" on the chord diagram tell you where to put your fingers, but you play all the strings except ones with an "0" - that is indicating that the string is silent. In the C chord they are telling you not to play the bottom string (however, since the bottom string is an E and that is part of a C chord it will still sound okay if you play it). A chord is several notes played together (C = C E G) and chords on guitar will have some of the notes repeated. From the bottom (thickest string) up the C Chord is actually (E - bottom string - not played according to the diagram) C(5th string), E (4th String), G (open 3rd string), C (2nd string), E (open 1st string). Moving the "X" will not allow you to play the chord higher or lower, it will change the notes and the chord won't work. A Capo (a device that clamps over the strings of the guitar) can be used to easily raise or lower the chords, but you probably be fine to play them as shown in the diagrahm. The chords are not the melody (they won't sound like the song by themselves). They are intended to be played while you sing the melody.