Chord boxes are fairly standard, but let's look at an example. Each of the chord boxes will show you a four- or five-fret area of the neck. As you can see from the following diagram, the lowest string is on the left and the highest string is on the right. Place your fingers as shown in the diagram on the appropriate pitches. Unless you see a small number beside the chord diagram, these chords are in the first open position (“open position” refers to chords in the first three frets that involve open strings). If you see a number beside the diagram, it means that the chord shape starts at that fret.
An “X” above a string means don't play that string. A “O” above a string means to play that string open. Pay careful attention to the Xs and Os when playing the chord shapes.