Higher extensions (9ths, 11 ths and 13ths) can added to all the scale tone chords in a key, simply by adding more 3rd intervals above the top note of each chord. Shown below are the scale tone 9th chords for the key of C major.
Upper extensions can be added to all the chords in a progression. Here is a II V I progression in C major using scale tone 9th chords.
This II V I progression in C major uses 11th chords. Notice that the 11th is sharpened in the two chords that contain a major 3rd degree, in order to avoid a clash.
This time 13ths are used for all the chords. Notice how adding different extensions changes the flavor, even though the basic progression is still II V I in the key of C Experiment with adding upper extensions to other progressions.