I assume you mean in a midi track - click on an empty track and select create new midi object and then select for example 'empty 4 bars', then double click this midi track and draw in your chords with the pen tool. you can then select which instrment you want to be played by the midi track
If you are talking about chords from samples (not midi) when you pick the sample there is a row of buttons along the top area of the sample menu. There buttons (numbered 1 - 7 ) are the chord progressions for that sample. Drag one of those onto your track and you are good to go.