I can only tell you about a 2014 Rancher but I hope the procedure for yours in similar.
Press and hold the mode select button and turn the ignition switch ON.
The maintenance indicator will appear and flash twice. After the two flashes, release the mode select button.
Wait, just found instructions for the 2008:
Press and HOLD the Select Button
Turn ignition ON
Continue to hold the Select Button until the oil change message disappears
Release Select Button
Turn ignition Off then back On.
Message should be gone.
I hope this helps you.