You need to select a chord root and a chord variance. I have provided a very limited selection of chords just for illustration, since each chord's definition needs to be hard-coded or looked up from the database.

Red dots indicate finger positions and give the musical note of the position. Small black dots indicate an open string; a black dot with an X above it means it should not be played at all (see for example C diminished).

Barred chords (such as F or A barred) are shown with the individual notes rather than a bar. It should be obvious that a bar is required when playing it (across the first fret in the case of F).