Kohler STERLING 402040 Homeowner's Manual page 4

Install the Push Buttons
Press the large push button in the center of the cover, and use
your fingers to carefully pull out and remove the small push
button. Then pull out and remove the large push button.
Press the large push button onto the larger diameter rod, and the
small push button onto the smaller rod.
Insert the rods into the side holes in the push button housing in
the center of the cover. Press down on the push buttons until they
click into place in the housing.
Flush the toilet several times using first one push button and then
the other to verify proper operation.
1058763-5-A 4 Sterling