how do you reset the oil life system?

Some GM vehicles have a button located in the fusebox inside the vehicle to reset the oil life system.  Others use a series of key on/key off switches such as holding the key in the on position for so many seconds, etc.  Check your manual or ask your dealer how to do this and they should be happy to show you.

Rather than guessing, I'll tell you where it is!

When you use the "Info" button to toggle the digital readout to "Oil Life" press and hold the "Enter" button (the
arrow) until the oil life resets to 100%.

Good luck!